While the standard itself doesn't enforce any encryption, you could write an RCS based app that encrypts messages between endpoints. There are SMS apps that do exactly that, you just have the other contact install the same app and scan a QR code.
> Yes, I'd much prefer that Google and the carriers both have the opportunity to read all my communications instead of one or the other.
And I'm saying, regardless of the current implementation, just because it's an open standard, doesn't mean it can't be encrypted -- either in-transit or end-to-end.
Asymmetric cryptography, e.g. the TLS standard, is an open standard but secure (re: encrypted).