Where do people get the idea that jax is a hyper carry?
Even if he gets through his horrible laning phase and somehow manages to buy his extremely expensive items, he has a horrid late game. Good luck diving a squishy when a 0cs support can make you utterly useless and pressing R simply makes last whisper/void staff more effective against you.
"but muh splitpush dueler!"
Why not play Tryndamere then? He doesn't have a terrible laning phase and can do everything jax does.