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)
Diaspora is actually worse for privacy, because of its distributed nature. Diaspora is about distributed ownership. If you value privacy in a social network, check out https://github.com/ssbc/patchwork