In the last few weeks the League of Legends Worlds Finals took place. One of the teams who made it to Round of 4 was GenG. Their midlaner is widely considered to be among the best in the world, and their team has dominated their region. Despite that, he hasn't won a single worlds. The team that won has the most legendary league player because when he shows up to worlds, he locks in and wins by any means necessary. T1 was the fourth seed in their region, and they were one game away from not even qualifying to worlds. But once they made it to worlds they locked in and won the whole thing.
I think one of the key issues with matchmaking in team based games is that they encourage solo queue instead of forming groups of reliable regulars. Having a regular group of people to play with also reduces toxicity and it lets you have clearer expectations of your allies. The power of friendship is undefeated in team based games.