Why do you need centralization for "network effects"? Send a cc mail to all people you want to communicate with, exchange keys in person and use PGP.
Worried about traffic analysis? Well, in that case don't trust Signal and send encrypted messages regularly (including fake messages) to some Usenet group, using mixmaster or Tor.
I was a PGP enthusiast for some time, and advocated it to technical friends.
In the end, though, I only ever received a single PGP‐encrypted mail from a single person.
These days, I have over a dozen reliable Signal contacts, nearly all with safety numbers verified in person, and have sent to or received from them hundreds (perhaps thousands) of encrypted texts and voice messages, and dozens of encrypted audio calls. The majority of my immediate social circle doesn’t use Signal (and some have tried and rejected it), but a sizeable chunk does use it, including non‐family.
When it comes to volume and quality of E2EE communication in my daily life, I cannot call PGP anything but a failure, and I cannot call Signal anything but a success.
Worried about traffic analysis? Well, in that case don't trust Signal and send encrypted messages regularly (including fake messages) to some Usenet group, using mixmaster or Tor.