Diaspora* is one that's been around for yeeeeears. A federated Facebook basically. I always wished it'd take off since I do like the idea of having a personal page for very close friends and my network but it is much harder to take off because, while reddit and other sites have tech-minded folks willing to learn and migrate, very few people have an entire extended friend group looking to figure out what a decentralized federated Facebook would entail.
The sad truth is that Diaspora pretty much refuses to federate with anything other than itself. Some projects have managed to reverse engineer the protocol, but you'd honestly have more luck with Friendica or Hubzilla. Even then, neither of those things are perfectly analogous to Facebook.
The thing is, he has some valid points. But, much of the fediverse have pretty much figured out basic interoperability, and now we're moving on towards more complex features in federation. Diaspora has, in my opinion, fallen very much behind everyone else.