XMPP had a fair amount of shortcomings and the real issue is that federated systems don't solve spam. So everyone living in this "we'll run our own IM systems,

XMPP had a fair amount of shortcomings and the real issue is that federated systems don't solve spam. So everyone living in this "we'll run our own IM systems, just like email" is deluded, as spam in email is barely a solved issue. And much of the solution involves blocking "independent" servers.