The long fight to make Apple's iMessage compatible with all devices has raged with little to show for it. But Google (de facto leader of the charge) and other mobile operators are now leveraging the European Union's Digital Market Act (DMA), according to the Financial Times. The law, which goes into effect in 2024, requires that "gatekeepers" not favor their own systems or limit third parties from interoperating within them. Gatekeepers are any company that meets specific financial and usage qualifications, including Google's parent company Alphabet, Apple, Samsung and others.
The carriers never bothered to implement RCS; they just outsourced the whole thing to Google.
That nobody uses.
It's meant as a replacement for SMS. It's not just some new version of SMS that Apple hasn't upgraded to, which is what you were basically saying earlier.
It's a messaging service used exclusively by Android phones. iPhones all support iMessage; Androids (mostly) all support RCS. All of those iMessages go over Apple's servers; all of those RCS messages go over Google's servers.
For what it's worth, iPhones have supported sending full-quality pictures to everyone over a legitimately open protocol since launch day. It's called email.
Google's attempts to legally force Apple to adopt its proprietary platform is transparently anticompetitive.