If they truly cared about sec, they would use something like Signal.
I don’t expect Apple to graduate RCS to a blue bubble, as it’s advantageous to keep the blue bubble “special”. I’ll be interested to see if society adapts and starts treating whatever RCS gets categorized as as “acceptable” or if we’re too far down the classism path for that to happen.
Why do you feel Signal is better security wise?
Even if you turn on e2ee for iCloud (“Advanced Data Protection”), your endpoint keys will stop being escrowed in a way readable to Apple in your backup, but the endpoint keys for everyone you message with will still be escrowed because they have not enabled Advanced Data Protection (because it’s off by default), so Apple will still be able to read all of your iMessage traffic.
99.9%+ of iMessages pass through Apple servers encrypted with keys that Apple has copies of (thanks to the insecure non-e2ee default nature of iCloud Backup). If the middle transit service has the private keys, it’s not e2ee.