RCS was an idiotic take from the start.

It's origin came from a good place. The wireless industry, not Google, started driving the standard to retire/replace SMS/MMS. However, then the wireless industry was reduced to a duo-culture and Google decided to drive RCS after many years of carriers/manufacturers trying to do their own thing to little success.

Another route: MMS could be enhanced to have some modern features while still being backwards-compatible. The datagrams are just XML and the syntax is akin to E-Mail. Larger message sizes could be supported, while the gateways still handle resize/reformat for older device backwards compatibility. There was even a format for a few minutes in the early aughts called EMS that had some promise but it died from disuse. Message delivery confirmation has existed since GSM and CDMA.

There's even a standard for IMS video calls that has been in the 3GPP stack since the 1999 release that would've allowed universal standard video calls. Since carriers hated building data networks and consumers weren't ready for video calls, it just sat stagnant until iChat AV/FaceTime came along and popularized video calls. It's still there, it could still be used.

Somewhere along the way, standards-based universal calls, video, and messaging took a back seat to tech bros and their proprietary stacks, and governments (at least the US) were too stupid and incompetent to understand what regulation was necessary to correct this path we are now on. Hopefully the EU can continue to help fix this.

It should've been a layer of encryption over SMS and remain otherwise stateless and platform agnostic.

Umm what?

SMS has a very short size limit. Implementing RCS as an encryption layer on top of it would require devices to send several messages just to cover a short one-word reply. They also often come out of order so they would need to include a numbering system so the client could piece them back together.

Granted that is already how SMS works on modern devices, but the underlying protocol is woefully inept at modern messaging and completely unviable for what you're proposing.

How should media attachments work? I assume you expect that to just use encryption built on MMS? So media can come through even more compressed than basic MMS? None of the actual benefits of RCS would be possible if it was built on top of the existing ancient standards.