Also, its simply false that the market has not produced good solutions and if there was a 'unified message solution' then people would cry 'monopoly' and demand government regulation as well.
The fact is that the standard tool for most people use for messaging in Europe is an incredibly secure protocol.
Has it really failed though?
iMessages supports CALEA (but is still end to end encrypted, as well as FaceTime), all US messaging products must support it (even Twilio supports it [1] [2]). You are unable to subvert nation state legal jurisdictions within fundamental telcom infrastructure. Signal can get away with it, Apple, Google, and cellular carriers cannot.
Can't have your cake (universal messaging) and eat it (end to end encryption with zero trust requirement) too. So can't we push from something better than SMS, using regulation if required? It must not be perfect, but simply extensible in the future (similar to SS7). In jurisdictions that are favorable to it, you support E2E encryption. In those that are not, you downgrade loudly. Compromises must occasionally be made.
[1] https://www.twilio.com/legal/law-enforcement-guidelines
[2] https://support.twilio.com/hc/en-us/articles/223136547-Submi...
So, the SMS solution is what these quasi-regulated entities gave you. Whereas iMessage, RCS, Signal, etc is what private industry gave you.