It's a draft XEP, so it's not widely implemented yet. I know the server I'm using supports it via a plugin, but I don't think even Conversations supports it yet.
The one thing I do think XMPP really has going on for privacy protection is that multi-user chats can be configured to not give out the real JID of members to other members, which is something I kind of miss in Matrix.
If the Block command is the network's only available abuse prevention tool, then chat network has failed to do a good enough of job of implementing anti-abuse protections.
(I'm aware that some people don't believe in network-level anti-abuse protections, and I'm not going to try to convince anyone to agree with me. This is just how I evaluate whether a given chat network is accessible to me or not. XMPP is one such network, and doesn't have any, so.)
Just to pick on this, sorry. The XSF terminology is not obvious (it was inherited from other standards organizations).
Draft here means the protocol is absolutely in use, it just means that it is theoretically open to changes. The next stage is "Final", and that is typically only reached after substantial time in production (it's basically a statement that the document is 100% finished and won't ever be updated).
There have been proposals to change the term "Draft" to "Active" or similar.
XEP-0191 is supported by practically all servers: https://compliance.conversations.im/test/xep0191/
And supported by all modern clients.