So, there's a few reasons autofill is the worst thing in the game.
First off, and many high elo players will agree, it is best to learn maybe 1 or 2 champions in the game, refine them, and get good at using those champions exclusively. A LOT of high elo players are OTP's. There's even high elo players who dodge/feed everytime their OTP is banned. So, Riot introduced the genius system that lets you pick your roles that you can play your champion that you're good at, and let you play those roles. You will get those roles, no more fighting over roles, you can play your champion where they shine. What a great idea!
So, who the fuck came up with Autofill? Why FORCE someone to play a role they're not comfortable in? One they aren't prepared at all to play? I get that queue times are sometimes longer because some roles are more popular than others. That's fine. 5 minutes longer in queue isn't going to kill anyone. No one expects to press a button, and instantly get a game. I'm okay with waiting longer, if it means I can play my champion in my role.
All autofill ACTUALLY does is get you put on a team where you're in a bad spot off the bat, you're struggling, you feed, you get flamed, and you're forced to play a 40 minute long game with everyone telling you how dogshit you are at the game and to off yourself. It literally ruins the game for 4 other people, and there's NOTHING you can do about it. You are FORCED to get autofilled, at least once. Autofill alone can ruin an entire game, and ends up being nothing but a waste of time. But I can still get reported because my team is saying I'm intentionally feeding because I don't have the confidence or know-how to play a role I was forced to play. How is that fair? How is that fun? Who thought it was a good idea?
Autofill boils down to "Hey, other people don't want to wait in queue, so you have to spend 40 minutes suffering now. Have fun!" It's stupid. And whoever came up with it is stupid. Just take it out of the game. If people don't like the longer queue times, they could learn a less popular role, or find a friend who plays support, or learn to have some fucking patience. You already spend 10x as long in the game as you do in the queue, so it's not like people queue up for a game and only have a limited time to play. And if they do, that's their fault.
Remove autofill. No one likes it. It's stupid. It makes people upset, and frustrated, and makes you feel like shit because you can't play ADC when you're a top lane bruiser main. Just take it out of the game, and stop listening to the idiots crying that their queue was 7 minutes long instead of 4.