There are some clients that support the latest version of OMEMO, but yes, since the most popular ones do not, you end up using the older version most of the time. That said, the older version is not generally unsafe, it basically is the same as WhatsApp or Signal are using. The newer version is just somewhat better as it includes some lessons learned from earlier attempts.

E2ee is not everything, as most of the privacy sensitive metadata can still be collected. Sure it is nice to have, but even more important is that you can chose a trustworthy server operator or run your own. XMPP allows doing that, but it has some weaknesses with client implementations and so on.

I am a bit biased and would say all in all XMPP is probably the best option right now, but it depends on your specific priorities. It certainly has some rough edges though.

Cockpit is a simpler choice for that.

Many people have not used XMPP in years or never and go by hearsay of outdated information.

Matrix on the other hand had several million Euros of venture-capital to fund a marketing campaign.