Really, asking "what should replace Facebook" is putting things the wrong way around.
A more interesting way to ask the question is, "what did Facebook replace."
People used to build their own websites. People used to have blogs. People used USENET which was truly distributed and un-censorable.
Facebook and Google took the open internet and open standards and monetized and made everything crappy. Enough of that. Nothing should replace Facebook, it's done, stick a fork in it.
@Hascobe @hhardy01 Exactly this. I have a blog. I'm never going to convince everyone I interact with on Facebook to join me there. I'm never gonna convince my mum that she needs to make an account to talk to me there and then get her childhood friends she's reconnected with to contact her there, too. Why would they?