It’s not that people are stupid, sometimes you’re simply talking to a teenager with no life experience. Often it is because people are kind of stupid. My national (r/Denmark) subreddit has devolved into a vile place for instance, I’d compare it to t_d, it’s the best “quick” comparison there is, but it’s obviously not as bad, at least not yet.
I think /r/space is the only major subreddit that I don’t dislike, and most of the smaller ones have been abandoned.
The new design being horrible was just what tipped the iceberg.