Have you seen signal's issue tracker? Ik it's a big project, but it's literally getting spammed, plus the desktop app that keeps database key in plaintext and won't work natively under wayland (needs xwayland, making basic stuff like sending attachments hard if you use most tiling compositor, tho that's partly Wayland's design flaw of lacking consistent reference implementation). Also I principally don't trust apps that rely on both proprietary network services and libraries. The very fact that they don't leverage their funding to reduce their costs by working on support for federation that is not a matrix bridge (which hasn't been even developed by them btw) or decentralization, especially since XMPP, SimpleX and Matrix (which has currently 3 well developed server implementations: Synapse, Dendrite and Conduit) have been able to do so with much smaller funding. And it's Signal, not Molly's maintainers who have been putting more effort into shiny UX improvements over hardening infrastructure code lately. And even if Signal does improve it's security, the patches get regularly backported into Molly, whereas even such basic shit implemented solely in Molly, such as app passwords that actually encrypt it's database is pretty useful. Because even PIN scrambling is not fully immune to shoulder surfing. Defense in deph matters.

tl;dr a longer rant about decentralization vs federation 👇

Even the argument of network effect achieved thanks to reliance on phone numbers is becoming less relevant these days, with DeltaChat providing a convenient way to have encrypted chats using the existing email infrastructure in much more convenient way than traditional PGP. Pixelfed has already achieved E2EE DMs and it's being worked on for Mastodon. If the UI of the most popular apps and the official web interface are also redesigned to make messaging more convenient to use it might have the same positive effect on user retention as Facebook Messenger once had. Anyway things are bound to change in favor of federation, but not necessarily decentralization. For instance I got mixed feelings about EU's DMA. I'm optimistic about the interoperability benefits it could bring, but even the official act doesn't specify how it'll be implemented. If it relies on something like WebFinger which does require a domain name it'll end up just grouping a couple of major walled gardens together, so for example SimpleX, Session or Status users still might not be able to chat with people on centralized platforms