There definitely needs to a an official rating system. People saying "Get rid of the system!" are silly. And people who want to change the existing system are wasting their time. The MPAA exists to service Hollywood, and it's doing its job.

The proper way to get rid of the MPAA is to make an official movie rating system that actually makes its way onto movies alongside the MPAA rating. Difficult, but not impossible. Then it's your job to convince people that the new system is more relevant, which you couldn't do if it wasn't in front of their face already because they can't be assed to care otherwise.

And then you can convince the theaters to enforce the age limits of the new system instead of the old one.