Anime is a medium. Of course 90% of it is meh to bad because that's what 90% of EVERY medium is like.
I feel like I keep seeing people complain about anime like it's all one big monolith rather than just another entertainment medium with a variety of different genres and subcategories within it. Action, comedy, fantasy, horror, slice of life, sci-fi, so say nothing about certain demographics certain anime fall under like shonen and seinin that also run the gauntlet for what genre(s) they'll be, or common premise tropes like mecha and isekai that be used in multiple different demographics and go for different genres.
This is NO DIFFERENT than how every other form of entertainment medium works. Cartoons, live action TV, movies, radio, theater, comic books, video games, novels, f**king puppet shows, etc. None of them are all one thing. Each one has a variety of tones, genres, demographics, and approaches to their name, and likewise plenty of crap to their name too that eventually gets forgotten about while the actual good stuff gets remembered, talked about, and passed forward into the future.
If you were to watch 1000 movies, you wouldn't even scratch the surface of how many movies exist, and you sure as hell wouldn't be qualified to declare that movies are unwatchable garbage. In fact most people would call you a moron or at the very least someone who is just looking to try and start arguments with others if you were to give that take.
And it's the same (or at least should be) with anime. It's just another medium but we'll still get people trying to declare that all anime except for a few select exceptions is just terrible and garbage and only people with no taste or ability to think like it. Because they themselves have no ability to distinguish any anime from any other, or they do but they just simply don't want to. They see it as all one thing and thus whatever small sample they've experienced (if any) works as a perfect example for what the entire medium must be like. Because it's easier to go to complete extremes than just talk only about the specific anime that they didn't like and it makes them feel superior because if they don't like something that many others do then that must make them so much smarter than they are.