The problem with hyper snowballing champions like Riven, Fizz, and other assassins
is not that there's no counterplay or that people don't know how to play against them.
The problem is if you mess up JUST ONCE, if you are out of position for even a second these champions can immediately capitalize on it, kill you, and start to make life miserable in general. And the worst part is most of these champs have a get out of jail free that they can use any time they're even close to being in danger of dying.
I know how to play the riven matchup and I know what to do to avoid dying but as a human, I am imperfect and will at some point get too close to her and then BAM ult flash stun qqqr dead and then she starts laughing over my dead body.
Champions shouldn't be able to punish mistakes easily and avoid being punished at the same time (see: Darius).
: I noticed you are out of position, i.e. stepped out from behind minions to try and do anything.