Right, and you don't enter a queue thinking "I'm going to get my primary role most of the time" when you and Talents(Prolly our current highest players) have both gone through streaks of not getting that primary role(And in talents case, not getting that nor secondary).
And that'll tilt diamond players, if they're given their cake and then have it snatched away because autofill. Honestly at Diamond+(High plat, even), role selection should be removed, and the disclaimer should be 'You're high elo enough. This is the real test. Either you know the game good enough to be up here, or you don't and will fall.'
And I think that's fair. Back in my hayday I learned to play all roles competently. When they introduced the role system, I veered mainly into top and sometimes mid, where if I tried playing any other role right now I would suck shit. So I say remove the role system for high elo-because it sets unreasonable expectations to the players, and players tunnel into a role in a way that when they're forced to do something else, they'll become tilted/tilt others/suck and lose.