Role queue actually lowers matchmaking quality.
A lot of high elo players are actually starting to notice this as a root cause: you don't have to be "as good as the elo" to be in that elo. What I mean is, it's so much easier to 1-trick or play 1 role all the way to a certain rank - but your actual understanding of the game is still very low.
So like before role queue - once you got into a Plat game, everyone would have an overall somewhat equal understanding of the game. Now, you get into a Plat game - and you know if you're going to win from champ select. People that are autofilled will probably have no clue how to play other roles because they will get their main role AND champion in 90% of games. So someone playing fill every game is probably better at the game than someone only playing one champion, in the same rank.
I think in actual high elo, maybe Master + - role queue should no longer exist. You need to be a good player to hit challenger, not just good at one champion/role. Straight up.