So I get a banned when I leave a ranked match?

I get banned form rank and take a serious penalty because I don’t want to watch my random teammate get destroyed and run the whole game. How is that fair? I died in swamp and he was all the way in market. Why do I get banned because the game thinks the character can get all the way across the map in 20 sec to grab my banner? I think that should be removed. It’s not fair to make me sit and watch a teammate who doesn’t want to be apart of a team. Not to mention I get a penalty for leaving? The ban sure, fine but to make me lose so much RP because I’d rather jump right into another game than watch my teammate for 30mins run around. Get this fixed. Broken game with broken rules