The story goes like this. I queue up for a lobby, I get my pre-selected role (one of) and someone leaves. I get into another lobby, I get my pre-selected role (one of) and someone leaves. This happens 3 or 4 more times and then I get a lobby where I am autofilled into support. EVERY. SINGLE. TIME. I am autofilled to support. No one leaves. I'm forced to play a role I hate and a role I have no champions in.
There should be an option to opt out of autofill. If I wanted to play support, I'd select it as my role. I'd happily queue for 10 minutes if it meant I got one of my preferred roles, and I'm sure A LOT of others would too, because in 95% of my lobbies where I get my role, someone is pissed off they didn't get their selected role.
Autofill is toxic and leads to a bad experience. Shame on you Riot.