>>47400512The reason it's rated so highly is because people were upset about Ai getting shanked.
I've seen dozens of comments from weebs talking about how it was the most upsetting thing they've ever seen in an anime, how it was the first time an anime has made them cry in years, etc.
I have to imagine that they're the kind of people who only watch the most generic happy ending FOTM garbage for that to happen, but even then Ai was barely even a character, so I don't see how anyone could have possibly felt anything for her.