We did replace it, almost 10 years ago. It was called Diaspora[1], no one cared about privacy then. No one really cares about privacy now, at least not enough to do anything about it. 1. https://en.m.wikipedia.org/wiki/Diaspora_(social_network)
I think people care a lot more today than they used too. The problem is people use facebook because they have to.
People are mad at FB the same way people get mad when they realize they've been in manipulative relationships, but I'm not sure many people really want to accept that they gave into that despite all the warning signs that have been there for years and it's their own actions which enabled FB to be what it is.
Some of the issue is the belief that anyone really needs FB. We've conditioned ourselves into it, but you don't need it any more than you need TV.