I am used on banning Yasuo so that no one in my team takes him, now i will have to ban yummi instead.
Every single one who picked this champ inted. And i can tell you why, as main support you might have noticed that on Plat elo and bellow it is very hard to find a decent adc to play with, so many times you have to carry the lane.
Now imagine picking a champ that is only capable of shielding and healing a bad adc. You can not cc you can not damage so everything is up to this bad adc. i can promise you that you will lose lane and both will feed and as support you will be the one to blame, even though it is not true.
So if you want to keep winning just don't pick this champ.