That's an understatement, my carrier has disabled MMS years ago. Still, that's not an issue with the MMS protocol, just an issue with carriers.

> That's a distinction without difference in the US.

The American carriers including Jibe in their network still speak RCS to clients. Google's Jibe is the most prevalent remaining RCS server but carrier Jibe isn't using the proprietary protocol that Google Messages uses (otherwise it wouldn't work on iPhones).

Looking at https://support.apple.com/en-us/108048, https://support.apple.com/en-us/118609, and https://support.apple.com/en-us/109526, carrier-based RCS is available in quite a few places. Nowhere near as prevalent as SMS/MMS hubs once were, but that has to do with the fact that in many countries SMS and MMS have been replaced by third-party apps over a decade ago.