What makes you think privatizing would fix any of that? It'd just be another Universal / Disney / etc. with overpriced foods AND overpriced admissions

Edit: And this also totally misses the point of the parks to begin with. They're there not just to entertain visitors but to preserve these landscapes for posterity. Privatizing them would totally go against that. We don't need anymore land barons exploiting the masses and preventing them from experiencing the places they have a birthright to.