TobThe sites themselves aren't the problem (generally)
Public pugs simply attract miserable people. The crowd nobody wants in their dmix servers
Some don't care. They'll feed 24/7
Some care too much. They'll whine whenever things go wrong
Combine the 2 on one team and you get a miserable experience for everyone in the mumble.
So both groups need to learn and understand how to play together
as alba said above
albathe reason to play is because tf2 is fun. Elo shouldnt be the motivator to play, that just leeds to toxicity.
In every mix you'll have person who plays better and person who plays worse or some people who don't like eachother. Even if you'll get 12 players, all of them from prem div there can be conflict between them but you should at least try to cooperate.
Idk why but there weren’t so many divides between people in the past (in old pugs)