If they don’t use Google’s extensions, people are in the exact same situation they are now, with text messaging between iPhone and Android being shit. They do support RCS on 18, btw.

And that’s the point. It won’t mitigate any of the complaints, because the actual standard that Google will match them on is not capable of any of the features people are complaining about not having, because RCS is still a fucking terrible standard. (iPhones do support virtually every other standard you listed btw, because they allow third party apps.)