Common Knowledge: Like many of Lovecraft's creations, Cthulhu was never portrayed in his stories as a particularly powerful combatant. He was intimidating because of the influence he held, his alien incomprehensibility, his near immortality, and the fact that his mere presence is a Brown Note, not because he could No-Sell conventional weapons or end cities by snapping his fingers. He wasn't even one of the stronger Great Old Ones. As a result his depiction here can contrast quite sharply with his image in pop culture. Indeed, of the eight unarmed and unprepared sailors who come across him he only manages to successfully kill three of them.
Death of the Author: Cthulhu is actually one of the only entities Lovecraft himself illustrated, where he (or technically, a statuette of him) is depicted as having multiple scattered eyes and a very rotund body◊. Almost all fan-art of Cthulhu tends to completely ignore this, usually giving him only two symmetrical eyes and having a slim or muscular body.
Harsher in Hindsight: The return of the Great Old Ones is described as when the earth would "flame with a holocaust of ecstacy and freedom". Post World War II, that line sounds a lot more frightening. (It should be noted that the word Holocaust before the Nazis meant "burnt offering to God," although it had been used in reference to genocides going back to the early 20th century.)
Hilarious in Hindsight: The story features a cultist named "Castro." A few years later, Lovecraft would befriend a different expert on lore named Adolphe de Castro.
Mainstream Obscurity: Cthulhu is easily the most well-known of the titular mythos' entities and, as the story where he is first introduced, The Call of Cthulhu is arguably Lovecraft's most well known work nowadays, but the pool of people who actually know of the story further than the title and that Cthulhu is in it or Cthulhu's actual relevance in the story is much smaller.
Memetic Loser: Cthulhu sometimes gets this treatment after people read the short story, as he was built by popular culture as godlike creature that drives people insane it can be a little Narm to see him defeated by a steamboat.
It should be considered a case of Technology Marches On, at the time of the writing a steamboat could be considered the largest vehicle and man-made object, if the story was written in the current days, a nuclear weapon could be used for the same effect, as written in the RPG game: "So what happens if you nuke Cthulhu? He reforms ten minutes later, but nowhe'sradioactive!"
While the colorful and vividly grotesque descriptions of various nightmares, alien cities and otherworldly horrors are indeed powerful, it loses a bit of its punch when the narrator describes most characters of colour the same way.
Among the many descriptions of the Old Ones, you wouldn't expect the word hilarious to appear.
The word "cruise ship" evokes very different images these days.
Paranoia Fuel: The cult still lives, and now you know too much.
Values Dissonance: The non-white cultists are described in terms that make them sound more like savage animals than human beings. Lovecraft's depiction of the cultists isn't much different than, say, D. W. Griffith's perception of "The Negro" in The Birth of a Nation (1915).
◊. Almost all fan-art of Cthulhu tends to completely ignore this, usually giving him only two symmetrical eyes and having a slim or muscular body.
