Well, if you can convince my carrier to embed XMPP into their texting network, I'd gladly take it over RCS. In practice, you can pick between "works on any phone" and "not designed for carriers".

Using the carrier standard is entirely optional. I only use it in extreme circumstances, like with outdated 2FA websites and when half a bar of 2G is all I can get. I like it that the built-in app will have modern features on any modern phone soon, but that's about all I feel about it.

If anything, the relative openness of RCS at least lets you write bots and other tools. There are a bunch of open source libraries that can communicate with RCS servers. Can't say as much with WhatsApp (outside of the EU) and iMessage.