The XMPP stories/comparisons are such bullshit, imho.
Sure, both Google and Facebook both used XMPP for a while (even at the same time, so you could message someone from Google on Facebook), but XMPP was an unpopular niche protocol before that and it’s still the same today. I used to be an uber (foss) nerd at the time but even for me the appeal was close to zero - although I’ve tried it several times.
I’ve also literally never heard of anyone signing up for Google or Facebook due to their alleged XMPP 3E strategy. Google Mail was already the most popular and most hyped mail provider and Facebook was at its height as the defacto quasi-monopolist social network as well - everyone who was willing to sign up with them had already long done so.
(Funnily enough, the Cisco in-house messaging and video calling solution we use at my work, through which we also receive landline calls, is still running on XMPP to this day, so I sorta became a XMPP user after all…except I haven’t started this software in 10 months because fuck landline calls and we have better alternatives for chatting.)