Elo system

In all honestly, after 5 seasons, how are we still using a poor ranking system. I get S or A ratings in a ranked game, and then get demoted in my division. How is that even logical? If ANOTHER player is the one feeding and hanging the game to the other team, why am I the one punished and dropped lower in rankings. You expect all players to carry in all games at all times? If that is HONESTLY what you expect to happen, you need to give lots more love to the support roles. This is getting to be insane. I lost 5 promos in a row, and then went all the way down and got demoted, with never getting less than an A rating.