Because not all players can play well with others who do not play on similiar skill level, just because a player is (X) rank doesn't mean they play exactly 100% the same way another player does and this is why it leads to toxicity, bad play, some players choose to verbally abuse, and therefore this is why I prefer TOP/Mid Roles in League because I don't have to put up with someone who just sucks in a lane phase and end up "Feeding" like hard.
Even in DOTA 2 after getting restrictions on League for about another week, I found myself feeding in DUO lanes hard because I feel players had no idea what to do, but I go solo lane and almost every game I went positive fast and did a lot more than I would normally do.
So the new Role System is going to help get rid of a lot of toxicity I feel and it will be great if the system matches players who "Duo Que" so players can play by themselves in a bot lane as two friends knowing how to play good together and what to take often reduces toxicity and uber bad play aka losing a turret in 10 minutes, been there seen that many times.
But to answer the question its supposed to help players reform but really doesn't understand the real issues of a game, for instance myself getting reported for "Feeding Hard" because of the awful forced roles, I can't wait until this new system because I know myself I can do a lot better.