Please no autofill in ranked.

I don't understand why autofill is a thing in ranked. We want to progress in our main role and we play said role because it's what we're good at or enjoy the most and when we get autofilled we are not only 1) potentially dicking the rest of our team unintentionally but also 2) Not gaining more than only 3 lp in our main role, and the rest of it going into a role we don't give half a crap about.

I had enough time for one game before work, lost that opportunity because of this problem. It's really annoying and I can't understand why it's a thing in ranked matches.