I see the matrix is more popular than xmpp, but why?
A more general chat platform will really want end-to-end encryption which IRC doesn’t have. Matrix & XMPP offer decentralized rooms so you don’t have to create an account & join each server to chat, but rather your server can connect to another server.
You don’t have to solve every problem in a single application. If you need privacy, use iMessage or Signal.
Public chat is by definition not secure, anyone can be sitting in the room logging, so it’s not that essential as long as client-server uses TLS. Modern IRC does have SDCC chat, but not all clients will use it, so stick to secure messengers.
iMessage doesn’t exist outside the US in practice. Signal is centralized, requires a SIM and a Android or iOS primary device (i.e. you must have a phone & it must use the duopoly OS) making it a low recommendation from me.
TLS is fine for an open, public room, but not all chat rooms are public tho. Folks DM each other too an a chat platform & their talks definitely shouldn’t be un-E2EE as it probably shouldn’t be the server operator’s business.
You don’t have to solve every problem in a single application.
I know what you are saying, but also why not? In the case of XMPP, it is meant to be extended to solve any communication task provided someone can engineer the theory into practice (which is usually a money limitation not a technical one).
If you can’t afford an iPhone, that’s tough, but I live in the US where it’s 56%, and around the world it’s 28%, which is not “doesn’t exist”. And in any case Signal exists for the others. Yes, if you use a freecycled GNU/Linux phone with not-sold-in-Shenzhen wireless chipset not supported by any carrier so it has to be hardwired to ethernet, you’ll have a harder time.
And if you do try to do everything at once, you fail at everything. Which is what happened after Google EEE’d and crushed XMPP, it’s unsupported in full by anyone. There’s no money in open source networking, it’s near impossible to fund the people who work on critical infrastructure, let alone new toys.
Meanwhile, there’s a system that’s been working for 35 years.