Attack on Titan sucks.
The characters are soulless robots with only the goal of pushing the plot in the direction needed for the story to continue, and having very little depth outside of that. The half-baked character relationships are a fatal flaw with AoT's character writing. There's never enough effort and time put into establishing the relationships between characters and why they'd actually care about each other. When you watch the scene where Hannes dies, you think "that's the drunk guy Eren knew as a kid and interacted with a couple times, so it's emotional and impactful for Eren to see him die", not "Damn, we will never get to see these two interact again on screen" which would make you feel the same loss the protagonist feels.
Most character arcs are just the character's flaw being established, and then one or two scenes showing them overcoming that flaw and becoming a different person. It's very cheap. The way character arcs are written never changes from season 1 to season 4, and most characters only have one arc at best.
Characters like Levi or Mikasa are bland, one note, and would be forgettable if not for their plot armor and fight scenes. Levi is just a generic shonen badass and one of the characters that doesn't even change from start to finish, not even undergoing the show's usual rushed character arc. Mikasa has the complexity of milk toast and the personality of water. So many opportunities for her to develop and grow, yet she remained stagnant and one-dimensional.
Most of the pre-timeskip worldbuilding is retconned via plot twists and doesn't matter after the timeskip. It's almost a different story entirely. The Survey Corps feels like it's set dressing and mostly an afterthought.
The crux of the narrative post-timeskip is focused on the morality of the Rumbling, yet there's not a single attempt to help the viewer sympathize with the outside world. There's no real in-universe reason for the viewer to side with the Marleyians. The outside world is so cartoonishly evil and shallow that the Rumbling is the only logical option, but then the story wants you to feel bad when a bunch of nameless NPCs are stomped on at the end.
The plot is an edgelord fest that doesn't hold up under scrutiny, which is why the fanbase hated the ending. Once they had confirmation that there would be no more plot twists to give the narrative more depth than a puddle, they hated it. The plot doesn't make sense because it's so focused on "recontextualizing everything" with every subsequent plot twist, that it's lost all identity. The entire show the viewer is made to believe that this is a post apocalyptic world with giant cannibal monsters, and by season 4 we transition to a WW2 allegory with terrible political writing and themes that are executed with zero tact or nuance.
It doesn't matter if it was foreshadowed, you don't go from giant zombie slasher to wannabe-game of thrones in the span of 60 episodes. The author tried writing two entirely different stories using the exact same characters and world, which is why the series has no identity outside of "plot twist after plot twist" and "edgy gore." It's also just a blatant ripoff of Eternal Champions, where the protagonist Erekose is given the "god powers" of his world and is part of the race Eldren, which were exiled and excommunicated from the rest of the world because of terrible things that they did in the past. And now in the present day, the world hates the Eldren and wants them gone, and Erekose has to find a way to protect his race from extinction using his "god powers."
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