The only people who still use XMPP in a significant capacity are the likes of Nintendo (for the Switch push notifications system) and it is pretty out of reach for any average citizen.
XMPP as a protocol for engineering and science is fantastic. As a set of standards it's well designed. Performant, flexible, and powerful. As a general, average Joe software however it fucking sucks big time. And it is precisely this flexibility that makes it suck. It's not just flexible, it's a mess. And mobile support in 2021 is atrocious.
There's a reason why Telegram's very shitty protocol is vastly more popular for average Joes than XMPP ever was.
XMPP was designed by engineers, for engineers. Which is good for this very specific set of engineering problems and essentially useless for everyone else.
Want secure communication? Use Signal, Threema, hell even Telegram is more secure in its default canonical protocol implementations than XMPP. And stop beating the dead horse XMPP is.