ULTRA SECRET STRAT TO DEAL WITH AUTOFILL
So, some of us hate being autofilled. We can't play more than a few roles, for better or worse. Or we hate having teammates who are autofilled, as we cannot play the position we are assigned to properly.
So here's the revolutionary idea- work with the people who you're playing with for the next 15-60 minutes!
You get autofilled to a role? Let your team know that you're autofilled! They'll be able to help you out. I've gotten responses ranging from "can you play jungle?" to "just do x and i'll be fine". Some of us are forgetting that our team isn't just a bunch of autonomous machines programmed to troll every single game. They will compromise and try to help you out so they can win too!
Even in cases where they won't switch, play a champion who is closest to your role. You play mages?
You play tanks?
You play marksman?
You play
? GO FOR IT! WORK WITH YOUR TEAM AND EXPLAIN WHAT AND WHY!
If all that fails, if your team is full of toxicity due to your Sion support, dodge. You are probably better off out of that lobby, as it most likely would've gotten toxic in some other way.
Edit: Another thing to note: Tone will impact your responses immensely. If you say "GG autofilled give me mid if you want to win nooblordzzz", you probably won't get a positive response.