One of the criticisms of Gnostisicm, even going back to the ancient Greeks is it never makes positive assertions about what the new world will be like. It's only negative saying things like "all this is illusion," "all this is bad." It never puts up its own program for criticism. So if you say anything about Gnosticism, the Gnostic can just respond, our faith isn't that, it's better than that. However, they never tell you what it actually is so it can be objectively criticized.