That was true 20 years ago. For the past 10+ years XMPP has had Stream Resumption that allows you to resume a few stanzas you missed recently (typically with a poor connection), and Message Archive Management that stores everything on the server that you can then retrieve on the client.
XMPP has had little place on the public stage, but that doesn't mean it stopped evolving.
XMPP has had little place on the public stage, but that doesn't mean it stopped evolving.