Guess you never used Celo. If 4 top 100 players go against 3 top 1000 and one 1 top 100 player, balance absolutely doesn't matter. And most 3vs3+ games are like this. You can nearly always determine the winning and the losing team before the game starts by watching at Celo.
You sound like those who say like "omg they have 4 prestige 3 lvl 100 players" and leave before game even started.
Balance absolutely matters in any game mode.
Nerfed obers, ISU-152, PTRS AI, JT, schrek long-range accuracy obviously had influence on solid % of wins.
I have managed to win with team of randoms aganst arranged teams several times so far.
Do you think balance doesn't mattered in these games?
Or do you think that such games doesn't contribute to winrates?