Does buffing and nerfing a champ always have to be based on how good they are in professional play?

I mean, I love and in my elo, he is perfectly fine (Silver, lol), even in plat or diamond he is fine. He is pretty decent when it comes to average gameplay, but in professional play hes op (high pick rate and high win rate). I seriously don't like how Riot still considers to nerf him despite being overall decent in casual play. I just recent bought a skin for him since hes so fun to play. And there is people like , where sometimes i'm confused why she gets nerfed. She is barely played at all too. I just wondering how Riot would nerf and already ok champion. He was perfectly fine until pros started to play him. He was underestimated on release.