All that matters is the worst player in the game. Whoever gets to lane against them gets fed and wins.
There is no opportunity for a A+ player to kill a B+ player, because the game is already decided when a C- player DUMPSTERS an F- player.
The problem is, it is OBVIOUS who the F- players are, but Riot doesn't account for individual performance whatsoever, so the entire team is punished for 1 absurd liability, and then the matchmaking continues to deteriorate.
In low ELO especially. It isn't a game anymore. Its a teammate dice-roll simulator.