Picked New Champions in Ranked

For what reason does Riot Game(s) allow people to pick any new release of a champion in ranked? I just had a teammate pick Yummi and lost us the game because their bot lane was just too ahead. Some may say that I could just use my ban to ban it, but why would I want to ban a champion because I am to afraid of my OWN team picking the champion. I'd rather use my ban on something that I don't want to play against.

A simple solution to this is to implement a system of where the champion is disabled for maybe 24 - 48 hours or even longer.