The degree of centralization is directly correlated with its reach. It was decentralized when most people in it were tech savvy, it became centralized as more people got in that are not tech savvy. To make it decentralized again we could 1) expel all non tech savvy people 2) increase the level of tech savvyness 3) create a parallel web where mostl people are tech savvy. I don't see either 1 or 2 happening any time soon. (3) is happening with bitcoin and tor, but as soon as they get popular enough they get centralized again.