It wouldn't be such a problem if there weren't SO many people who did have the 'mid or feed' attitude. I'm thinking more and more that if you want to queue for solo play, they should start using the role selection system like they have in mmo games like WoW. It would be imperfect, and it wouldn't be final but say when you queued you listed any roles you were willing to play:
If you were willing to support, you'd find a match real quick, if you were ONLY willing to play the more desired roles, you might have to wait.
Enough decent players would put down all 5 roles, but if someone got 'stuck' with support or jungle or whatever enough times and really just wanted to top or mid for a game, they could put down those roles for a game selection.
This obviously is an imperfect system, but I think it could work better than what we have now. (The firewater)
There would also be a gamemode such as blind pick where people can go other types of roles such as two ad carries bottom etc.
I also understand that there would still be trolls selecting all the roles to get in then trying to play a different role, but there really is no end to trolls is there?