One of my longer-term goals is to integrate Mumble on XMPP (others have thought about this too) since its chat is pretty shit & needing accounts to join isn’t great but or two good foundational protocols.

XMPP is better for modularity which is why everything is at extension with means the foundations are simple & easy to implement where you can build something optimized & bespoke on it like Fornite’s coms or Nintendo’s presense. It’s a little harder to understand tho since out of the box you get almost nothing—but the big servers intended for chat like Prosody & ejabberd have sane defaults.

The centralization you are referring to seems more a client issue since the protocol & servers already ‘do the things’ but it sounds like you want a single ‘app’. For community building where you consider group calls less common, both Movim & Libervia offer more than Element (note the other Matrix clients are lacking feature parity) since they both can do integrated posts like forums—where Libervia supports calendars/events too. There’s no reason a client couldn’t exist with Jitsi or Mumble integration.

Ultimately use the right tool for you—it’s just nice to dispel myths that Matrix has some special sauce or that predecessors can’t fill the same roles (while also using less resources in all directions).