if apple didn't do it's shenanigans, RCS or something similar with a
different name would've have replaced MMS by now.
The only reason there's any RCS interoperability right now is because most carriers have bought into the Google RCS stack. Before that you absolutely had to be aware of which carrier the recipient was using. If memory serves T-Mobile is running both a Google and non-Google RCS stack. RCS is and was a mess.Hell, if you've a rooted Android you can't access Google RCS and any RCS messages sent your way will disappear into the ether.
If you want to interact with the RCS world as a non-wireless carrier, expect to pay upwards of 10 cents a message and have a minimum revenue commit of thousands of dollars a month. Carriers also don't get paid for inbound texts on RCS, creating a huge new cost center instead of symmetrical texting volume resulting in minimal costs like the current SMS/MMS ecosystem.
This is a dumb complaint honestly. The carriers and Qualcomm closely control the standards bodies and could address this problem. Instead they focused on the bag-of-garbage that is RCS, which Apple has finally said they will support. But because RCS is a bag-of-garbage, Apple plans to support a different flavor (the basic standard) from Google's. $0.50 says Google will magically start supporting the basic standard too once Apple ships it.