Disable players from queing for ranked
Its a simple suggestion, sometimes you're going to have a bad day, where you just can't win unfortunetly players don't know when to take a break so they perform terribly and bring other players with them down.
My suggestion is putting players on a cooldown for ranked que once they lose 5 matches in a row. Once you lose 5 in a row it's time to give yourself, and your team mates a break. That's all.