Ah yes, a whole group of relatively balanced champions should be sledgehammered by nerfing their core items because Riven abuses them better than other people do. It's definitely not that high level Rivens have near infinite mobility, animation cancels to do stupid dps, two stuns, a shield, and a multitude of ways to deny counterplay.
And by the way, Riven has a crit build as well as the fighter type build and they're both nuts, so she is most definitely the issue. Not saying items aren't sometimes the issue (old Stormrazer), but what you're saying is basically the equivalent of people saying Iceborn is the problem and not Ezreal even though tons of tanks use it and it's balanced for them.