Purpose of role queue mandatory support games for divine+ players?

So this is a question I have asked myself and my friends many times lately. Usually it is after a game where support player is obvious smurf player who does some sort of quick calculation that is this game winnable or not and if he comes to the conclusion that it is not winnable he will troll possibly from the first mistake his core makes. They don’t care because they know they will win their core games more often than not.

So the answers I have come across why there are mandatory support games: Faster queue times and people should learn more roles to become better player overall. Well I understand the argument that players certainly should test every role and every hero in the game, but what level of undying pos 5 skills do one need to posses to be a great mid player.
Second argument: faster queue times. Well this is just a nobrainer for me, do I want to queue pos 1 for 10min or even 20min and get a solid game where everyone is committed to their roles or do I want these sub 5min queues where I get pudge pos 5 leeching xp behind me in the bushes with occasional range creep hooks and to play possibly 4v5 game for 40min and get -30mmr and then if I win next game I am +-0 mmr, with probably 1,5h-2h considering queue and playing time and also I have 2 more games to go before I need to play a role I am not that good at.

Long story short, if anyone got good explanation for these role queue game grinds plz share.