No joke, you've got to do something about the pre-game lobby.
I'm legitimately tired of having three people call ADC, somebody else locking it, and then having one of those other people then rage and lock in ADC anyway just to intentionally throw the game.
It's amazing that people can legitimately be turned off of your game before they've even started playing it and have no reasonable alternative to getting punished for it. That's really not a good sign.