Here is what I've come up with playing 1 game at a time random through the day:
1. If someone is level 50 and instantly starts telling everyone what to play, leave game. They'll probably be the one sucking most.
2. If someone's mic is open for the entirety of the countdown period, leave game. The noise will only get worse.
3. If you want to win, play with friends on a consistent basis. I can't really do this right now as all my old gaming friends are scattered, and I can't find most of them after this many years of not gaming.
Despite the annoyances, I'm still having loads of fun. I really haven't explored many characters yet. I basically play Junkrat, Reinhardt, or Mercy because I feel like I'm contributing when I do so (while enjoying myself).