Yeah RCS always has been an embrace extend extinguish thing. The carriers were super pissed to lose their SMS revenue to WhatsApp and iMessage so they came up with this shit to be an active partner in the loop again, and they can bill for it again. Consumers didn't fall for that and it died off.

Unfortunately Google revived it but it's a very poor standard for interoperability. Not only because the lack of true E2EE in the open spec but also because you need to be a blessed party to run an RCS server and communicate with others. You can't run your own or choose a party you trust. It's either your carrier if they bother to run one, or Google.

It's just another power grab. Don't fall for its 'open' guise. They want you to use it so they can make you dependent and lock you in again. There's nothing open about it. If you want privacy, use signal. If you also want an open and federated network, use matrix or xmpp with OMEMO.