This normal game match up system is really stupid

what is the reason having separated normal game mmr? I really hate this system, its the end of season, and when i tried to play for sometimes, I always have plats and diamonds in the other team, and having bronzes and silvers in my team. I don`t think my mmr is high, i know im tarrible, but it is not even close to close game, the team just gets rekted. they are saying this is because they dont play normal games often, but what is the point for higher ranked players massacring lower ones? I think rito need to make some fair match up system which is acceptable to everyone.