When are bad players going to be banned?

The biggest form of toxicity and the underlying cause of it are bad players. Keep them out of ranked games and leave them in Norms or Bots. I would rather have someone who curses every other second, then someone who doesn't know how to last hit minions, or understand what it means when you're all alone in the middle of the map with the wards, or feeds the enemy team 0-1000 and then say gg.