The problem with the Gnostic movements like the Cathars was that they promoted a more personal approach and mystic attitude which took the power away from the authorities. Most societies don't see any value in teaching people how to become enlightened on their own. It frees them, makes them independent, and empowers them so it's not possible to exercise so much poitical control over them.
That's why all mass religions are pretty much equally useless, because they're meant to be. It's not for religious reasons and has nothing to do with religion. The early Christian movements, or the Gnostic movements, is how Christianity should have been or could have been if it had been allowed to flourish as it began. It was based much more on the pure teachings of Christ and also incorporated many elements from Eastern faiths, like reincarnation and karma, vegeterianism, etc.
What people think of as conventional Christianity is pretty useless, but most can't see past that, or even imagine there's anything else to see.