ugh

I'm good at one champion. When I play that champion, I always win. I usually get about 15 kills and 1 death. I'm bad at other champions. When I play any other champions, I lose miserably. I usually get about 1 kill 15 deaths. I don't want to level a smurf just so that I can try out other champs. I am not going to wait 20 minutes just so I can do a team builder that gives me different mmr.

Why can't riot just give me different mmr with each champ when I play normal or ranked games?