Riven is not a difficult champion to play. If anything, her kit allows more room for error.
She virtually has nothing to worry about.
She doesn't need to worry about mana. She doesn't need to worry about cooldowns. She doesn't need to worry about being caught out. She can outduel most champions with her ult + BC and she can 1v1 due to her kit.
I'm tired of this meme that Riven is a difficult champion to pull off. She's really not.