Arguably false. Are you trying to imply that Apple users are the only common users of messages other than text or that Apple users use third party messaging instead?

Lots of providers implement RCS, lots of people use it. Perhaps none of the people in your particular region/circle of contacts do? My contacts almost all use signal. The exceptions where there are people that don't have any third party messaging apps, they use RCS. To those people, it's "just like a better MMS", they don't know any different, it just improves their messaging with no effort.

At least for the region I know, there are _a lot_ more Android users than iOS users, and third party messaging is really common. In practice, SMS is the last resort if you have nothing else.