The promise of XMPP + E2EE (with OMEMO) is appealing, but I found that in practice it doesn't work. For example: you want to start an E2EE chat with your friend on the riseup.net XMPP server. You can't, because their server hasn't enabled the necessary XEPs like Message Archive Management.
I think XMPP is perhaps the best example of what Moxie was talking about in The Ecosystem is Moving: it's a super fragmented experience. Most users do not (and should not need to) know the technical details of how their server, or their friend's servers, are configured.
I like the speed and simplicity of XMPP with OMEMO, but you're right that apps and servers may not all be up to date. IMO, if a server doesn't support the latest IM and Mobile compliance suites[1], the admin responsible is negligent, though. You should just be able to install Conversations and have an encrypted chat with anyone (I recognize that this is not, in practice, the case).
For me, the biggest blocker on XMPP is that OMEMO and multiple devices don't seem to get along. Matrix solves this with cross-signing, but I don't believe the OMEMO XEP addresses the problem in any way.
I think Moxie's article is directly a response to XMPP. But on the other hand, Matrix has managed to have both federation and rapid evolution, so he's just empirically wrong.
May I suggest you give it another try? It has been steadily working for me for a few years now. (Conversations/gajim/dino/siskin-im/beagle for the clients, and prosody server side)
> because their server hasn't enabled the necessary XEPs
Changing to a server that does is not a big deal, since most (all?) XMPP clients allow multiaccounting.
> it's a super fragmented experience
What you call fragmentation I would call diversity, and I think it is a good thing.
> Most users do not (and should not need to) know the technical details
I agree that a certain level of abstraction is necessary to use complicated stuff. However, I think not having the slightest idea of things work is a problem, and leads to alienation.
I think XMPP is perhaps the best example of what Moxie was talking about in The Ecosystem is Moving: it's a super fragmented experience. Most users do not (and should not need to) know the technical details of how their server, or their friend's servers, are configured.