Highlights include Sliding Sync (instant login/launch/sync), Native OIDC (industry-standard authentication), Native Group VoIP (end-to-end encrypted large-scale voice & video conferencing) and Faster Joins (lazy-loading room state when your server joins a room).
“Joining XMPP” is a low bar. I’m talking about it having a viable, usable alternative with features that people are used to expect.
You mentioned siskim as the best alternative for iOS which - looking at the main page and open github issues - does not seem to support reactions or group messaging. In 2023, this is not acceptable for anyone but the most hardcore apologists.