It's a voluntary activity people do to have fun and relax. There is no point in whining. Just go do something else if you are not enjoying yourself. Kids often don't realise that and get generally overinvested in things so we somewhat excuse their immaturity. It feels less tolerable when it's an adult doing it.

Doesn't matter. If you invest time in a game (maybe even in a competitive or "ranked" mode) you expect that everyone in your team is playing seriously. People who don't shouldn't play this mode or game. What you call "whining" is legitimate. If you don't play you are wasting your teams time, taking them hostage. Sometimes you can't leave a game because other penalties occur.