The protocol is worse for privacy
‘Trust me bro’
The problem is, you’re comparing apples with orchards. Analogous would be: ‘email is worse for privacy than yahoomail’. Plus in this scenario yahoomail only lets you send emails to yahoomail addresses.
Phone numbers are no longer required iirc
Phone numbers are still required to register and maintain an account. Only difference now is you can choose to hide it from other users and give people a ‘username’ to look you up with instead.
Matrix and XMPP are not alternatives and are worse for privacy and security
XMPP is exactly as good or bad for privacy as the servers and clients you choose. It’s a protocol, not a service. Unlike Signal, which is a brand/app/service package.
Conversations for android is an example of a good XMPP client.