Small social sites are just as dangerous in another way, as vessels for a toxic monoculture. Pro-anorexia forums, political radicalization, there was even a famous one that fetishized infecting people with HIV.

To add, a lot of the most infamous Internet subcultures, with the worst effects on the "real world" (think incels, /pol/ types, mass shooters) have their own forums or hang out on places like 4chan/8chan. Where there's no big tech corporation or finely tuned engagement algorithm. Just broken people finding a place where they can reinforce each other.