Exactly. Yes, Prodigy, Compu$erve, and AOL died out, but that's because people moved on to other stuff, which these days means Facebook and Twitter, though back then it meant internet services like email and USENET. People have basically exchanged one group of crappy closed centralized platforms for another. Facebook and Twitter will probably die out eventually too, just like MySpace has, after people move on to yet another group of crappy closed centralized platforms.
People move to the latest fad; at one time, open internet was the fad, and killed off Compu$erve and friends, but it didn't take long for MySpace and then Facebook to rise up and start displacing email as a communications medium. People don't care about open and decentralized, they only care about what's new and hip and flashy.