I can't speak for anyone but myself, and I don't hate anime--creatively, I probably couldn't live without it--but damn is it a medium that gets tiring.
First of all, I really wish anime/manga creators (can the "manga" part just be assumed?) would get over the obsession with sex and particularly women's underwear. I've seen anime where a character will literally draw attention to a girl's underwear for no reason other than because... the writer wanted to mention it. It's almost like an autistic reaction.
And it gets really, really weird too. Like, anime is bad about writing kids as having libidos, being really into seeing nudity or touching boobs even if they're explicitly ten years old or younger. Weirder still is that anime writers think that every species finds human women hot or sexy. Goblin Slayer is a recent example, but what weirds me out more is I've seen so many anime where an animal finds a human girl sexually arousing (and I'm talking meant-for-kids anime like Doraemon or Sailor Moon).
This brings me to another thing that begins to bug me... anime (and really most Japanese works) are very human-centric. What I mean is, in western works you have stuff like the Cthulhu mythos that posit man is actually not the center of the universe, or Hitchhiker's Guide where Earth is "mostly harmless," and many other metaphysical and philosophical concepts that can only exist if you're capable of thinking that maybe, just maybe, there are things beyond mankind.... but anime never ever does. Humanity is always special, and our every little feeling and emotion is something that should be cherished and respected.
In fact, whenever there IS an outside force, its always bad because hoomanity is speshul. Just look at JRPGs where the final boss is God. Just once, I would like to see them acknowledge that maybe letting an outside force help us out a bit might not be a terrible idea (because humanity choosing its own destiny has worked out SOOO well).
In fact, just in general I wish Japanese writers were capable of thinking outside the box.
Japan is really good at EXECUTING ideas... but only after a westerner has thought them up. Japan rarely ever comes up with an idea all its own. Just look at JRPGs... an entire genre that only exists because a couple of Japanese nerds really liked Wizardry and Ultima (both invented by Americans).
And even when they're handed a blueprint to work from, they can't think outside the box. Just for example, western Transformers cartoons quickly realized that the audience didn't need the robots to hang around with little human kids, and that you could take the concept kinda seriously or give the robots themselves interesting personalities and backstories.... but then Japan does their versions and oop, here comes the annoying human kids to be audience identification characters, because it doesn't even occur to these sheep-people that such characters aren't even necessary and maybe even detract from the experience.
Of course, its rare for a Japanese writer to write people as anything other than a vague, easily-transplantable archetype. Your average harem series is a good example.
Full seriousness, while all those "teens solving mysteries" shows Hanna-Barbera made in the 1970s are obviously cribbing from each other, there is a lot that makes them distinct, give them a unique identity. Alexander from Josie and the Pussycats is not exactly the same character as Shaggy from Scooby Doo.
In anime though? Pretty much 90% of anime is just the same twenty or so characters being recycled--often even down to the designs--wholesale. This is because Japanese writers don't think of characters as people, but as "types." I actually recall once reading that manga authors don't even always come up with character designs, but actually have templates or stencils that they can buy in stores that have the work already done for them (or at least, that's how it worked back in the day. Nowadays I'm sure these tools are built into computer software).
(I wish I could find that article again.... some western comic artist was in Japan, had to sit through a lecture from a Japanese boss about how westerners were "lazy," but then she went to a store and found that their stores sell the afformentioned pre-made characters and even entire page layouts. She bought some, took them to that boss, and basically said "what was that about being 'lazy' you slanty-eyed fuck?"--okay, she didn't say that last part.... if anyone has a link to that article, please post it)..
The thing that bugs me the most is that Japanese media seems unable to ever really broach or discuss actually interesting concepts or philosophies. It's always the same stock messages over and over--messages that I'm sure are deep to a Japanese person, but to westerners are the kind of thing you could get from an episode of Care Bears.
Compare to western literature. Don Quixote is an examination of the place of idealistic morality and the follies of trying to apply the logic of fiction to the real world. Watchmen is about moral quandaries in the face of imminent disaster. As mentioned, Lovecraft's work asks fundamental questions about the very state of the universe.
Even our capeshit comes up with interesting metaphysical concepts, like the Crisis on Infinite Earths, or Marvel's universe being a living being. I think the last time I saw anime do anything even approaching this a 1990s movie (I think Akira) ending with the implication that a character had caused a second big bang and created a new universe.... but again that was literally decades ago.
I mean, it says a lot that even something like Star Trek: the Motion Picture is the kind of story whose themes and substance could never be the product of Japanese culture. Hell even 2001 A Space Odyssey is beyond them.