There are two main views on the show as a whole: either it really hit its stride when it moved from a show composed solely of crude, shock-value humor to one focused just as much on social/political satire/commentary, or it completely went to hell by turning into an Author Tract.
Among those in the former group, there's disagreement as to when the change became visible. Any season between 3 and 5 is not unusual to hear cited.
The fandom became even more fractured as later seasons began incorporating season-long story arcs. The thing with South Park is, though, that it can sometimes be as polarizing to its fanbase as it is to people in general. Combine that with a town full of people and the tendency for things to stay relatively the same despite earth-shattering events, and you end up with a show that can have half its fanbase loving how it's using a character/joke/plot/etc., and the other half hating it, meaning the whole thing is constantly a Broken Base, over any number of issues from any given episode.
"You're Getting Old" and "Ass Burgers". Many fans weren't happy with these episodes for being overly dramatic, derailing the characters (especially Stan), and ultimately led to absolutely nothing but more of the same, while bashing both Stan and the audience at the same time.
"Ass Burgers" also got some flak for saying that Asperger's doesn't actually exist, with people being split on whether the characters saying it (namely, a bunch of people using Asperger's as an excuse to be assholes) were supposed to be right or not. The Season 22 episode "Buddha Box" came under some similar criticism for its handling of anxiety disorders.
The show's increasing reliance on topical episodes. Some fans embrace this, while others miss the episodes that consisted of original plotlines that weren't Ripped from the Headlines.
As of late, the morals of certain past episodes, particularly those focused on environmental activism, have retroactively created quite a bit of controversy. "Douche and Turd" and "ManBearPig" in particular have been singled out for promoting political apathy and dismissing the reality of climate change, respectively. Fans have harshly debated whether the whole show is guilty of promoting problematic messages or if episodes like these two are aberrations. It says a lot when Trey and Matt went and apologized for their depiction of Al Gore and went on to make a two-part episode to show that ManBearPig is indeed real and a very serious issue (Al Gore is still portrayed as an Attention Whore though, albeit one that was right).
In general, fans argue whether South Park was better as a lighthearted, yet vulgar Monty Python-esque sitcom, or the darker social satire of later episodes.
Season 17 has also caused this. Apart from the widely-loved Black Friday trilogy, some have pegged it as one of the worst seasons due to its shorter length and overly topical nature, while others cite it as an improvement over the last few seasons.
Season 18 in general can also be considered this with a few episode exceptions some fans finding it more topical and less funny than season 17 and having a continuing story while others think the continuing story and more topical nature improved it.
Season 19 continues the previous season's more topical approach to comedy and fans are still divided as to whether or not it made the season smart and more focused or just draining. In particular the season's focus on "PC Culture" and modern social justice moments, proved to be a big divider. For some the season tackled the hypocritical and self-serving attitudes of modern progressivism (and neoliberalism) in a smart way that few other shows were able to. Others feel that it was a very arduous and Anvilicious diatribe against the people trying to fix the social inequalities inherent in America while overusing Strawman Political caricatures.
Made worse due to the fact that years after his introduction, PC Principal is still around and Trey and Matt have introduced even more characters that represent or ridicule PC culture (like Strong Woman and the PC Babies). While the former may have more or less calmed down since his introduction season and has a smaller role since, some fans feel the PC Culture era has overstayed its welcome and that Trey and Matt are now beating a dead horse whenever they feel like it.
Season 20's jabs at the Alt-Right. Some feel they're a perfect counterpoint to Season 19's satire by hitting the flip side of the coin and tackling modern bigotry in a way that's seldom handled as well in other shows. Others feel that putting the objects of ridicule from Seasons 19 and 20 on equal ground is a Golden Mean Fallacy, with people on either side decrying their portrayal as inaccurate. Much like Season 19, Season 20's deliberate parallels to the extremely hot button issues surrounding their release is liable to set off quite a few arguments. Also not helping Season 20's point is the fact that the girls are blaming someone who hasn't done anything to them.
Then there's the way Season 20 was handled in general. Some people feel that dropping the episodic nature of the show in favor a serialized approach that focuses on a few set topics (i.e. the Alt-Right movement, the 2016 election, Internet trolling) is Trey and Matt continuing their evolution in terms of storytelling that started back in Season 18. Meanwhile, others felt that this approach results in a major lack in humor when compared to earlier years. Still, others feel that Season 20 started out strong, but that its dependence on the outcome of the 2016 election made the last few episodes horribly backfire.
"Timmy 2000"'s Take That! towards Phil Collins. While making fun of celebrities is par for the course for this show, and Collins is a rather divisive figure in music, many felt their reason for targeting Phil Collins was far more petty than others, which was the fact that "You'll Be In My Heart" beat "Blame Canada" for best original song at the Oscars. Some pointed out if they really wanted somebody to blame for being snubbed, it should have been the Academy. Not helping matters is that they have another Take That! towards Collins in South Park: The Stick of Truth, meaning that they're still bitter about it 14 years later. Some were okay with it, but others were accusing Trey and Matt of being sore losers. They've also played two Peter Gabriel songs in the show in a much more favorable lightnote The "Book of Love" cover in "Tweek x Craig" and "Shock the Monkey" in "Raisins", feeding into the Vocal Minority elitist opinion of preferring Gabriel to Collins.
Their critique on Donald Trump has been this. Some fans don't mind either because they seem him as an acceptable target or because they attack everyone. Another group of fans think the jokes have gotten old and feel the show is beating a dead horse with the heavy use of plots or subplots focused on critiquing him and wish they would just move on to something new.
The decision to make Heidi irrelevant again after breaking up with Cartman for good is quite contentious with the fandom. Either it’s a good choice that brings the show closer to its roots without the unnecessary relationship drama, or does it completely undermine Heidi’s character growth by treating her as unworthy of contributing to later stories, thanks to not being Cartman’s plus one anymore?
Season 23 has been generally received fairly well, but there are some elements that make it divisive. On one hand some are annoyed by the over-reliance on Randyand the Tegridy Farms story arc wearing out its welcome, after Trey & Matt stated they would not do serialized storylines anymore; on the other, relying on minor characters in the second half alienated other viewers. Other topics of contention are an underwhelming and forgettable 300th episode (after the epic two-parter and Continuity Cavalcade that were "200" and "201"), overuse of meta-textual humor (with Randy representing the show's creators and their decisions), the controversy on the topic of transgender athletes that several reviewers felt was handled poorly, and some episodes like the one with Butters and the Mummy, perceived as weird for the sake of it (reviewers reading it as a Take That! to Trey Parker's then-recent divorce doesn't help), with nothing particularly insightful or amusing about them.
Butters's prominence. While most do like his character, some still think that he's overused to the point he's the de facto fourth boy instead of Kenny, who has been largely Demoted to Extra. It doesn't help that a new episode in Season 26 was scheduled to air on March 22 (Kenny's canon birthday) only for it to be a Butters episode, which didn't sit well with Kenny fans.
