really need to allow people to mute others pregame/ postgame

I'm not sure if it would be as easy as you think - to my knowledge the pre/post game chat is a completely different system as in game chat - that's why it took so long for them to add it in to the reform cards.

Regardless, I think they should work on this as well.

And add to the matchmaking something called Prime system which some games have, which is filtering trolls from actual players who want to win. Current matchmaking will put a 30% winrate player together with a 80% winrate player. This way the 30% one will never try since the 80% one will carry for him and the 30% one will never improve unless put under a pressure.