Maybe, just maybe, nerf Riven ...
I don't have to mention that she is a high skill level champion? Why is she 53,22% winrate and 13,14% playrate? I don't believe that 13% of players are her otp or mains.
The issue here is her e and itemization. She can build Death Dance and Ninja Tabi vs AD, which makes her kinda immortal vs ad. Just attack her with ad champion when she has those items, you will see what I am talking about. Also she can itemize vs ap too. If she has such a good itemization, why isn't she nerfed yet? Riot, just do your job and balance the game.
I play champions that are high skill cap and when they are over 50% winrate and have high playrate, then something is not right. They become stronger than anything if you play right. Keep high skill cap champions below 50% so that they are kinda balanced.
Don't overbuff Riven, Yasuo, Shaco (my boy btw), Irelia, Akali, Neeko, Zoe, Sylas, Jayce (even tho he is kinda a stat stick), Rek Sai (she was good anyways), Zed, Ahri, Vayne, Lucian. Those champions are always kinda viable, even if you don't make them stronger than 50%. They will still be played and will be good enough.
who has had a high winrate for a while but will nerf
for same problem riven is having (at least according to a riot person who likes to tweet instead of post on boards) but for a shorter amount of time and a bulk of it was conqueror change.