I'm with you that Matrix is bloated. But XMPP has no default encryption and most clients are just super bad, which makes XMPP unusable in these times.
I'm waiting for (better) encrypted messaging on Nostr.
XMPP and Matrix are two competing federated end-to-end encrypted messengers. XMPP is far better, on server cost decentralization, speed over Tor, degoogled push notifications, multi-identities, and overall privacy. So if Matrix is inferior centralized bloatware, why is it more popular? Especially among techies, who should in theory understand these concepts.
This brand new video gives a quick overview of the technical reasons that XMPP is the gold standard king of federation. And it briefly discusses how Matrix manages to push it’s agenda:
https://video.simplifiedprivacy.com/xmpp-vs-matrix-why-matrix-sucks/