I love XMPP, but UX is a client-side concern, not a protocol problem (although some protocols make it easier/harder to have good UX). Both XMPP and Matrix could have great clients, although i personally find most Matrix clients to be more polished than XMPP clients (at the price of much higher resource usage for Element due to Javascript crap).

Some polished XMPP clients include dino/gajim (desktop) and conversations/siskin (android/iOS). If you're looking for a unified-brand client/server distribution, snikket.im is a pretty cool project and could use help and funding.