There is no reward for playing well.

[Curisu]

Or more accurately, my biggest complaint is that the worst player on the winning team gets infinitely more rewarded than the best player on the losing team, and the game frequently picks VERY unfair teams.

That's how competitive team PvP is. You have that in every PvP game and you can't "fix" that issue.

Sometimes you lose and sometimes the other team wins.

You have to play many round's to make statistics work in your favour.
But when you really play better then everyone else then eventually you will rank higher and win more.