There's also the inconvenient truth that a very specific part of the world was online in the 1990s.

Primarily more educated, more liberal, more wealthy.

Turns out, when you hook the rest of the planet online, you get mass persuasion campaigns, fake genocide "reporting", and enough of an increase in ambient noise that coherent anonymous discourse becomes impossible.

I mean, look at the comments on Fox News or political YouTube videos. That's the real average level of discussion.