The intelligence of Neanderthals is the source of a lot of discussion. The level of toolmaking of both species was at roughly the same level, but it seems Neanderthals never made any kind of art or jewelry, at least not one that could have survived. There's some evidence of Neanderthals and Homo sapiens living side-by-side for quite a while and possibly even forming joint societies. Why exactly Neanderthals went extinct is also not completely certain, some theories suggest Homo sapiens were better at procreation, other say we were better at the adapting to changing environments. And there is also the possibility that we simply got lucky.
Other evidence shows Neanderthals did have some art. Some research suggests it was the end of the ice age that did them in — analysis of Neanderthal sites found that their diet was approximately 90% protein and that they lived on large mammals like the mammoth, woolly rhinoceros, etc. — a good survival strategy in the ice age, where large mammals like this were common and abundant, but afterwards, when these animals went extinct, Neanderthals couldn't compete next to Homo sapiens, with our more varied diet.
It has been shown that people with Eurasian ancestry do have up to 5% of their gene pool inherited from Neanderthals. It is likely that there never really was an extinction — Homo sapiens simply absorbed Homo neanderthalensis by intermarriage. As Homo sapiens outnumbered Homo neanderthalensis by being able to produce greater numbers of surviving offspring, this is a likely outcome. Those two species resembled each other so much that if you gave a Neanderthal a shower and haircut, dress him in decent clothes and teach him the basics of the modern society, you could not tell him apart in a big city. So all Caucasians are in a sense descendants of the Neanderthals.
Artistic movements. Numerous ones like impressionism, surrealism, dada and postmodernism. While they were very modern (or even postmodern) and controversial when they were introduced, the fact that they've been around for ages means that it's often hard to understand why the movements were so important.
Greek paintings and sculpture. Most of it looks a bit primitive and even uncharacteristically unrealistic today, but without it literally all of Western art the way we know it wouldn't exist (maybe aside from a period of truly Germanic art at The Low Middle Ages).
Robin Williams and his mastery of Rapid-Fire Comedy and physical and verbal humor were once new and exciting, like having Groucho and Harpo Marx in the same person. (Mork & Mindy never would have survived without it.) Thirty years later, this same style of comedy has become a punchline in and of itself, most notably in a SNL Celebrity Jeopardy! sketch where "he" is told, "For the love of God, SHUT YOUR MOUTH!".
Stand-up comics. Most original and groundbreaking ones seem less so a generation later—or less—when their styles and gimmicks are widely reproduced. It can be difficult to understand what makes, for example, Lenny Bruce or Richard Pryor so important when stages are saturated with comedians who do approximately the same thing, many of them at least as well.
In Britain, comedians like Billy Connolly and Jasper Carrott were radically different from the traditional working men's club comedians in the 1970s who stood at a mike with a beer in hand and told jokes. Now their observational comedy and conversational style is the norm. Not that they're unfunny now, but they can seem like very conventional establishment figures when once they were radical.
One interesting thing of note about the working men's club comedians is that they themselves were a victim of this trope at the time. Beforehand, British stand-up was very stiff upper lip, with a guy in an evening suit standing motionless on a stage with very little charisma. As controversial as the racist/sexist acts of men like Bernard Manning would eventually become, they really were the benchmarks that every up and coming comedian tried to copy.
The work of many of the comedians of the "alternative comedy" set of the 1980s now often looks as quaint as the earlier comics they were reacting against, when viewed in context of later work.
Surrealism, non-sequiturs, and a rambling rhetorical style are so widespread among stand-up comics of the late 1990s / early 2000s that it's easy to overlook how influential Eddie Izzard was when he first coined that style. And even he simply imitated what certain American stand-up comedians and Monty Python did decades earlier.
Jerry Seinfeld's observational stand-up routine was insanely popular in the late 1970s and early 1980s, and it was widely recognized as fresh and original. Johnny Carson famously gave him the "OK" sign, when Seinfeld first appeared on The Tonight Show. Fast forward a few years and Seinfeld had become the go-to impression of a lazy hack comedian, due to being copied to death by lesser comedians. As early as 1985, a recurring sketch on Saturday Night Live featured a group of these, dressed alike and beginning and ending nearly every sentence with "What is the deal with..." and "I wanna know!" Seinfeld was also the first person to joke about airline peanuts, now pretty much synonymous with "lazy comedian".
UNIX seems to fall victim to this trope. Multitasking and on-line documentation are now standard, and the command-line interface is admittedly difficult. But clunky as it was, a person using a computer interactively was a major breakthrough in the early to mid-'70s when the computer world was still based on batch processing. The command line was actually considered user-friendly, believe it or not.
GNU plus Linux was considered revolutionary because it was a free full UNIX-like system that could run on a single off-the-shelf PC. Other free UNIX-like OSes have since been ported to the platform (particularly NetBSD, which aims to be incredibly portable). Even then, GNU plus Linux wasn't the first version of UNIX that could run on a PC. (That said, it's still more popular than other free UNIX-like operating systems.)
Computer programming languages can be like this. Older languages tend to have fewer built-in tools, forcing one to manually program a lot of things that newer languages take care of automatically. This causes many of today's younger programmers to write off these older languages as needlessly complicated to code in, without realizing how, for instance, C (introduced in 1972) was immensely more user-friendly than the programming tools that had come before (such as machine code and assembly language).
Usenet. In a world where any schmuck with an Internet connection can start a blog or a message board, this has gone from "groundbreaking innovator" to "place where only spammers frequent" very quickly.
The Gopher protocol, which organized content on the Internet into a browseable (by a text menu interface) hierarchy of sites, files, and folders, complete with a search engine has been all but lost to current generations of Web users as the direct predecessor of the Web. However, a decent-sized gopher space does still exist on the 'net to this day.
Commercials with the Trix Rabbit (where the kids deny him the cereal because "Trix are for kids") may have been funny once, but modern viewers are starting to see those kids as rather cruel and selfish in the modern day, certainly not the ideal role models for the target audience.
People these days, with handheld computing devices such as smartphones, electronic book readers, tablet computers, etc. probably don't remember the Newton MessagePad, the grandfather, so to speak, of many of these, and direct ancestor of the iPad. Quite a few of them very likely would think of them as unwieldy or clunky, but when they were introduced in 1994, they were far ahead of their time.
They were too far ahead of the time, which is why they were unwieldy and clunky (even by 1994 standards). When Palm came along and did the same thing, with much less ambition, they were unbelievably successful.
Technologies in general. Remember how a bunch of gigabytes were supposed to take up an area the size of a floor tile? Yeah... take one look at modern terabyte storage devices and hard drives and try not to laugh at those prospectives.
Computers were marketed based on their speed. It was the quest for 100, then 200, then 300 megahertz. By late '90s half a gigahertz and then one gigahertz finally arrived to a universal meh. Now only do-it-yourselfers and PC enthusiasts focus on speed or process specs.
Science. Theories that were once revolutionary are now things that are taught to anyone with a basic education, and many people who were geniuses of their era and had what was the best and strongest theory at the time now seem to believe things that are ridiculous. Even though we remember Galileo, Newton, and Aristotle, it's strange to most people to think how revolutionary their ideas and experiments (thought experiments or otherwise) were and how far ahead of their time they were. There are doubtlessly an even larger number of scientists, mathematicians and philosophers who have been outright forgotten by history because their work is now obsolete or factually wrong, or just became common knowledge and now exists in the work of later people who improved upon their original works.
It's telling that these days, a lot of stories of historic scientific geniuses are told more as parables of how stupid the majority of people used to be as opposed to how brilliant the scientists themselves were.
The above is the rationalization used by some who promote ancient astronaut theories. They express shock and disbelief that such "primitive" cultures could have possibly created complex structures, governmental systems or works of art without the assistance of a higher, alien influence.
In less than a decade, we went from cell-phone commercials advertising the ability to send photos or text messages as if it was magic, because it really was an innovative thing, to a time where the idea of owning a cell-phone that can't do those things is unthinkable. Cell phones themselves became examples over time, from their size (they used to be the size of a brick and just as heavy) to their service (they used to only work in high-traffic areas, and would be useless in the suburbs, for example) to just how many people had them. There was a time when, even after they got smaller, had wider service areas and lower rates, when well over 50% of the adults in the western world still didn't own one, and the idea of teenagers having their own was about as likely as aliens landing. A majority of households still had a landline home phone line, and wouldn't think of getting rid of it because that was their primary phone while their cells were (supposedly) strictly for emergencies. In the modern era, most households have one cell phone per person, many don't have landline phones at all, and when they do, they barely use them.
While being uglier, costing more to own and operate, and being able to do much less, the cell phones of yesteryear had battery power that could last for nearly a week, even when used heavily. Modern smart phones die in mere hours even with light use. The modern battery life is largely due to the 'feature war' between smartphone manufacturers, to have the brightest screen, the fastest Internet, the slimmest battery etc.
If you're too used to DVD and Blu-ray, watching a movie on a VHS tape seems... weird. The quality might seem grainy, the sound is lower-quality, etc., and there's all sorts of damage that could have been done. Plus, having to fast forward if you wanted to see a certain scene... and knowing they weren't that accurate, as most VCR systems would play about a second of silence and then pick up when you fast-forwarded or rewound.
And in this day and age, the fact that theatres or rare TV showings were the only way to see old movies seems kinda silly. In 2011, people scoffed at the idea of The Lion King being re-released in theatres... whereas just fifteen years previous, the practice wouldn't have been that ludicrous.
Pre-VCR, it was common practice to re-release movies to theaters just before a sequel came out. Disney themselves would re-release their more popular animated films every seven years.
For those who were around when VHS was the dominant medium, this trope is somewhat mitigated by the fact that VHS was always noticeably poorer quality than broadcast TV; and let's be fair, there was a reason why Laserdisc was the (albeit niche) choice for serious cinephiles in the pre-DVD days....
It's also somewhat exaggerated by the larger size of most modern-day TV screens by comparison to what was normal in the '80s and '90s; the actual resolving power of the eye at normal viewing distance means that for smaller screens, higher resolutions are not normally as noticed.
Whilst now-normal HD pictures looked amazing a few years ago, they now look much less impressive when compared to watching in 4K.
The grocery store chain Piggly Wiggly is the 'trope maker' of the modern self-serve grocery store, but most people likely have forgotten that. (Even fewer people remember that it was one of the first businesses to use the "just-in-time" model of production, and even one of the first to use the shopping cart, but that's because to most people, a grocery store is simply a place where you can buy food.)
A&P was one of the first chains to popularize private-label "store brand" merchandise (most famously Eight O'Clock Coffee), which is now all but universal among grocery chains.
McDonald's consistently ranks at or near the bottom in rankings of fast food franchises despite being the one that first codified the business model of a fast food joint, partially because it can't stand out in the status quo it created. That said, they are still #1 in profits by a decent margin, probably out of how utterly ubiquitous they are. People who routinely trash it still eat there at least once a month. (They do have to have something to legitimately complain about, y'know.)
Howard Johnson's and Holiday Inn were two of the first chains to really standardize the concept of a hotel chain as we know it today. Things such as on-site swimming pools, meeting rooms, and on-site restaurants that most motel patrons take for granted became the norm with Ho Jo, but Executive Meddling in the 70s and 80s, combined with a saturation of the market, pushed that chain into near-irrelevance. (Holiday Inn, however, managed to revitalize itself in The '90s.) Between the saturation of the market and the rampant rebranding present in the motel industry, many facets of the modern hotel that most people don't think twice about were seen as new, convenient, and groundbreaking when they first came out in the 60's or so. A traveler back in the 50's probably would've been blown away by the concept of a motel offering a continental breakfast, for instance.
The Toyota Prius, the first commercially successful hybrid car, bolted Toyota into the 21st Century, proved Japanese automakers were a force to be reckoned with, and almost single-handedly launched the Hybrid car revolution... and is now quickly becoming irrelevant and a victim of its own success, as the explosion of hybrid cars it helped launch has given rise to bigger, faster, and even more fuel efficient hybrid cars, with even other cars from Toyota like the Camry and Highlander Hybrids stealing its thunder, and leaving the Prius with less of an edge, and less to recommend it. And Toyota playing up the Prius's advanced technology, cult-like following, and general quirkiness for marketing purposes isn't helping, leaving it pigeonholed as a zeerust-y nerdmobile.
To a lesser extent, the BMW Neue Klasse/5-Series. When it first launched in 1962, it was revolutionary, being the first midsize BMW built since World War II and their first car ever to not be powered by a modified motorcycle engine, and a breath of fresh air in a luxury car market dominated by overpriced and oversized limousines and personal luxury coupes with massive, inefficient engines and boat-like handling, being small and light, with compact, high-revving engines and things like four-wheel independent suspension and unibody construction. Thanks to this, it singlehandedly saved the company from bankruptcy, established BMW as a major player in the global car market, and became the Trope Codifier for the modern compact executive car. Now, the 5-series too has become a victim of its own success, losing ground in terms of build quality and driving dynamics to similar models from rivals Audi and Mercedes and also foreigncopycatsfrom the Americans (Cadillac CTS), Brits (Jaguar XF), Japanese (Lexus GS-Series), and Koreans (Hyundai Genesis), as well it's own stablemate, the smaller 3-series, making it a shell of its former self with not much to recommend to it while remaining the market leader and still having a devoted fanbase.
Boeing Model 247, the first modern commercial airliner that first flew in 1933. Unfortunately, it was promptly joined by competitors using basically same technology but were just slightly better—most notably, the Douglass DC-3—that hardly anyone knew about the Boeing plane even in 1930s.
Memes in general. What was considered funny and viral back then can quickly become a Discredited Meme when beaten to the ground. For example, the "I was an adventurer like you, then I took an arrow to the knee" meme from Skyrim quickly fell out of grace weeks after the meme was born. With enough fervor, memes can become overused, tired, parodied, and hated within days. Whilst many memes became popular ironically, they then get taken on as being seriously appreciated by the media, and dragged into the ground well beyond the point where the original fans have derided it as an old meme. A notable example is "Gangnam Style", which due to being such a oversaturated mainstream meme at the time, will lead to groans from pretty much anyone nowadays rather than appreciation.
Jean Robert-Houdin was a French magician in the 1850s who invented the cliched Victorian magician idea. At the time magicians were seen as beggars, thieves, or children's entertainers, seeing one dressed like the finest of gentlemen, on a stage, performing for high society, was revolutionary at the time, so much so it's still most people's go-to image of a magician 150 years later.
David Blaine also fits this trope. At the time, Blaine's minimalist presentations of simple tricks with ordinary objects for unsuspecting people on the street was unheard of. A decade later it's a cliche used by almost every average teen magician as a substitute for actual presentation.
Bureaucracy is hated by almost everyone nowadays, but when it was first invented it was a revolution in fairness compared to the arbitrary rulings of family-run businesses that it superseded.
The same is true for the saying "An eye for an eye" and its many variations. Before it, justice didn't exist so much as arbitrary punishments and in nearly all cases, someone of noble standing would get off with much easier punishment, if any. Being punished the same way the crime was done and societal standing being irrelevant was completely revolutionary. Nowadays people only see the aspect of "So if my daughter gets killed by a person, in return their daughter should die?" Another interpretation is that it was introduced to prevent the problem of escalating blood feuds (Alice accidentally breaks Bob's leg, Bob cuts her head off, Alice's brother kills Bob and both of his brothers, Bob's father traps Alice's entire surviving family in their farmhouse and burns the place down...) that caused chaos in earlier societies.
Jokes based around current events tend to get this reaction after a while. For instance, seeing jokes about Michael Jackson being a pedophile are hard to laugh at now that he's dead.
Gaming magazines that featured partial walkthroughs would seem like a scam today, but at the time that was popular, that was probably your only way to get help on a game.
The Addams Family pinball machine was absolutely groundbreaking in its day, and nearly every pinball machine released after it would follow in its footsteps. It popularized goal-based gameplay (complete objectives to reach the Wizard Mode; before, pinball machines just had you continue playing until things were unlocked), use of magnets on the playfield, modes that could stack, and easy multiballs (prior, multiballs were made very difficult to reach and was itself an end goal). In other words, The Addams Family was the first pinball machine to have rules that intricate. Compared to the machines with more refined rules, better Competitive Balance, and more complex playfields that would be released later, it would be hard for a modern curious player to understand why The Addams Family sold so well when it looks like any other pinball machine, only rougher around the edges in gameplay and with less impressive music.
Anyone getting into pinball nowadays will eventually find access to the older electromechanical machines. In almost all cases, they will find them utterly boring compared to the more modern solid-state driven machines: Those electromechanical machines have no ramps, no pre-recorded audio (and thus no voice clips or music), play rather slowly due to their more primitive machinery, and had absolutely brutal difficulty, to where a standard game had 5 balls instead of today's 3. But back in their own time, these electromechanical machines were incredibly popular (albeit in a legal gray area) because not only were they at the cutting edge of electronic gaming, they were dirt-cheap to play. People could insert in a nickel or a dime and play, and if they were good, they could play for a while.
And pinball in general easily falls into Seinfeld Is Unfunny. Its nature as a physical device limits the types of gameplay, stories (if any), and artistic diversity that video games can have, so it can be tough to imagine a time when video games were so technologically primitive that Space Shuttle's scale model was so impressive, it yanked the market share of pinball machines back from arcade video games. That being said, the real-life physics of pinball is so complex that only in the mid-2010's has home computer technology become advanced enough to accurately replicate pinball virtually. The end result is Seinfeld is Unfunny becoming a Cyclical Trope for pinball, as the gameplay of pinball is nothing like any modern video games, causing an uptick in non-virtual pinball's popularity due to curious video gamers seeking them out to play.
The Prince by Machiavaelli. While it has a cold-hearted reputation, it is actually a guide on how best to govern with reason and make pragmatic decsions. While shocking in the Renaissance, the modern reader will consider most of to be sensible advice and not get what all the fuss was about.
Education and degrees. In the 20th century, just having a high school degree opened up a lot of doors for you. In the mid to late 20th century, having a college degree in the right field was practically a golden ticket to employment and job security. Fast forward to the 21st century, and holders of college, university, and even graduate degrees have become a dime a dozen and are finding it harder to get their foot in the door than their parents and grandparents did with the same qualifications.
This tragically applies to all fields, not just soft sciences. At first, one could be the snarky Hard on Soft Science specialist and study STEM fields for a guaranteed job in the field. Nowadays, it varies. While Doctors and Scientists are still always welcome, Engineers and Technologists don't quite have the same luck or at least, not without competition for the few jobs needed in the field within the same area. Turns out that when 1500+ graduates in tech fields go after about 50+ jobs in their local city, there's going to be a bloated market for areas that just don't need as much. Tech majors have to get especially lucky and hope that whatever particular field they studied in (programming, databasing, security, et al.) is going to find a job in their hometowns or else its relocation if they can even afford that!
The I.Q. test — what is commonly ignored is that the average must always be "100", and that if the average appears to be going up or going down, it's actually reset back to 100 — meaning that if you tested "average" in the seventies, you might be considered to be below average (or worse) today.
The ancient Romans connected their empire through a system of roads. It's been centuries since anybody found that to be new. Though, to be fair roads of any quality approaching Roman ones are actually Newer Than They Think. Even when railroads were becoming common few roads outside of cities where paved let alone as smooth as Roman roads. Most of them were still in use by the time cars came around and made wider roads necessary.
The establishment of democracy and the republic was not a new thing in the late 18th century, as it had existed in Ancient Greece and Rome, and likewise many Italian City States, the Netherlands, the Polish-Lithuanian Commonwealth and Switzerland but the general belief was that a democracy or a republic could only govern a small area of land. For a large area of land, only a kingdom or The Empire was feasible. It took The American Revolution and The French Revolution to first put the idea that a democracy can conquer, centralize and administer a large nation state in a time of self-centered monarchies. Nowadays most of those monarchies are republics.
Although later historians likened The French Revolution as a failed utopian experiment that anticipated The Russian Revolution, all of the ideas of the French Revolution, especially those envisioned by its most radical representatives — universal male suffrage, anti-racism, people's right to protest, abolition of slavery — have become entirely mainstream and written into the UN Charter. It was over a course of 100 years before every other Western nation started catching up to its program (and also going further by extending franchise to women) to the extent that it's become hard to see why the Revolution was so radical to start with.
Likewise the concept of nationalism while regarded as Patriotic Fervor and taken up by conservatives these days, was originally a radical leftist program of France to create a culture separate from its monarchical beginnings. This led to national festivals, national flags, national anthems and national holidays honoring prominent days as was as institutions honoring intellectuals and cultural treasures, was first put together in a single package this period. Today it's become totally traditional flag-waving and institutionalized so it's hard to appreciate what made this idea new, especially since nationalism while initially inclusive and internationalist gradually became exclusionary and expansionist.
In general, democracy as we know it (one man one vote) while widely cherished internationally as an ideal today, even by conservatives, was once considered a pipe dream argued only by impractical dreamers and regarded as quasi-Utopian. Even the Founding Fathers likened it to "mob rule". The vote was scrupulously restricted to property owners (all white and male naturally) and nations like England and the United States didn't widen the franchise until well into the 20th Century. It's become such a given that it takes some getting used to accept the fact that it's only in the recent era of history that democracy (full universal suffrage, men and women) was truly practised on what was originally regarded as an utopian scale.
In the aftermath of the American Revolution, it was decided that the ruler of the United States should be called "president," rather than king. It was intended to be an extremely humble title, and had previously been used mostly to describe someone who temporarily chaired a small meeting. These days, most countries have presidents, and the title is now so closely associated with being the powerful ruler of a country it may be considered ostentatious or presumptuous for a leader of a small organization to title himself president. Even the phrase "Mr. President," initially chosen for being the humblest possible way of referring to the office-holder, is now often used as a way to mock the pretentiousness of a low-ranking president.
Modern day nutrition, medicine, conditioning, and materials technology has radically changed the performance of athletes today in all professional sports. As a result, when one looks back at past greats, their achievements may not look as impressive in a modern context. Kurt Browning was the first figure skater to land a quad jump in official competition, in 1988. Nowadays, quad jumps are considered a standard part of any male figure skater's program. John Elway, hall of fame quarterback and back-to-back Super Bowl champion, is considered one of the greatest quarterbacks ever, yet his stats would appear quite pedestrian by today's standards (his career passer rating would have made him the 28th best quarterback in 2014, out of 33 qualifiers). Anyone who watches a player from decades past and declares that he "wasn't even that good" needs to be reminded of this trope.
The opening ceremony of the 1998 Winter Olympics had five choirs, one in each continent, along with performers in the host city of Nagano, singing Beethoven's Ode to Joy, together, in unison, live. This astounding feat can now be replicated by any group of people using Skype, if they can compensate for the lag.
The lighting of the Olympic Cauldron has reached such a level of one-up-man-ship (firing an arrow in 1992, lighting a zip-line in 1996, lighting a ring of fire that rose up to meet the Cauldron in 2000, the Cauldron bowing down to meet the lighter in 2004, running through the air to the Cauldron in 2008...) that the spectacle of lighting a cauldron itself isn't enough anymore.
Almost every innovation in sports can soon become this. Be it Sabermetrics in Baseball (or indeed any form of statistical analysis), the offside trap in soccer (to the point where you wonder why they even show a replay for such blatantly obvious offside as was common in the 1970s) jumpshots in Basketball, the "Kempa-Trick" in Handball (throwing the ball to a teammate who catches it mid jump and throws a goal before landing) or the forward pass in American Football. Sure those things "made" teams and coaching legends at the time they were first brought up, but now not having a smattering of those "tricks" would be patently ridiculous.
In American sports many of those innovations were brought by rival leagues to the established major leagues. There is a reason one of the documentaries on the upstart American Football League (whose merger with the NFL gave us the Super Bowl) is called "full color Football" - before that Football was hardly ever on television and mostly black and white. The AFL also started the wide open offensive style Football is now known and loved for. In a similar vein the upstart World Hockey Association gave a chance to a seventeen year old Canadian by the name of Wayne Gretzky and revolutionized the sport far beyond the few franchises that were merged into the NHL, but watching archive footage from them today seems... bland.
Propeller aircraft — for decades, they were the only air transport there was and even a flight from London to New York often involved refueling stops in Suddenly Significant City s like Gander, Canada or Shannon, Irelandnote which coincidentally contains the oldest duty free shop in any airport in the world, but today jet aircraft has replaced them on almost every route safe a few "short hops" — even though until well into the 1990s jet engines were actually less fuel efficient than propellers.
As space technology advances, older books and films about robotic missions from previous decades can seem a bit dull in comparison to more recent missions— it may seem hard to imagine people being excited about grainy black-and white photos taken on a brief flyby of a planet or moon if you've seen high-resolution color photos of the same place from landers and rovers. (Such as the hype about the Viking Mars probes in Cosmos: A Personal Voyage compared to the images from the Pathfinder mission in the 2000 "Cosmos Update" epilogue on the DVDs.) But those older photos were the first close-up glimpse of those worlds at all, and without them, the modern missions could never have been attempted.
Action Park in New Jersey helped revolutionize American amusement parks, especially water parks, in The '80s. To this day, many of its attractions are still radically unlike anything ever seen. Few people remember this nowadays, though. Instead, when the park is mentioned, it's remembered for just how dangerous many of those rides were before later parks managed to work out the kinks in them. Ask a New Jerseyan of a certain age about Action Park, and they'll tell you that it was either the most badass amusement park ever made, or a Real LifeAmusement Park of Doom that should never have been allowed to stay open as long as it was.
Fan conventions. In an era where cons (especially gaming and anime cons) pop up for just about every little thing (including My Little Pony and Power Rangers), it's hard to explain just what was so revolutionary and important about Otakon, Gen Con, or Comic Con. They're still fun and important, but lack a certain gravitas that they used to.
Worldcon suffers from this as well. In the 1940s, it was a big deal and was "the" event of the year within science fiction fandom, often the largest con of the year through the 1970s and 1980s, and generally featured some of the best authors, etc. on panels or giving speeches. Now, though it still occupies a prominent place, it's been far overshadowed by cons such as Dragon Con (which can be 10-20x larger and attract "bigger" names).
Going back further, it can be hard to understand why the World's Fair would have people so excited they came over from other continents, as it had no focus and looked like just another traveling carnival, only bigger. Events like these were the ancestors of today's conventions and expositions that focus on more specific topics and cater to fans.