XMPP were lacking "gamification" tools that'd encourage people to do better. Eg. for TLS there is https://www.ssllabs.com/ssltest/ but for XMPP it was only recently that https://compliance.conversations.im/ sprung to convince server operators to upgrade.

Also, clients. https://conversations.im/ is good for Android . https://dino.im/ looks like a promising Desktop client but where are the iOS clients? Stuck in XMPP dark ages from what I've heard.