Its best to use a protocol that doesn’t allow unencrypted messages
This is an implementation thing and not a protocol thing. What protocol doesn’t allow unencrypted messages? I am sure signal’s protocol would still allow it, it’s just that the implementation doesn’t.
And same for XMPP. Just go with the implementation that doesn’t.
Please show your work. What is the proof that it was done to consolidate power?
This isn’t to mention that your use of the word authority is strange. How exactly do you determine who has more authority between a US house representative vs. a CEO?