This is Google's end game messaging app. They want to replace text messaging and Google hangouts/allo/chat... were never going to cut it.
Its a chat app that doesn't look like one. It looks like the default sms app, you don't need anyone to download or make an account for it. There biggest hurdle was getting iOS users. They've now pressed apple into supporting it as well. They even have Apple state Google will help with their installation. We know Google pay apple billions every year to keep Google search the default on iOS, it even binds Apple to publicly and in court support the arrangements. I wouldn't be surprised if Google has paid billions just for RCS on iPhone. It will keep their marketing monopoly in place for a long time.
I agree. You're much better off just using Signal. It's not federated/decentralized, but all client apps, the protocol and the server code are completely open source and anyone can fork the project. It also works on every platform, its encryption protocol is the most secure one out there and it's been around for over 10 years. They also recently added some cool new privacy features.
Sure, but in my experience it's not that hard to convince people to get on Signal. (Maybe because here in Europe everyone already has like 15 messengers on their phone, so it doesn't bother anyone to download another one)
If you use SMS, you can argue that Signal has much better photo and video quality, it can be used from a tablet or a computer and it's basically just like iMessage but for all platforms.
The thing is is that if MNO's truly cared about running their own RCS network (instead of leaving everything to Apple and Google). It might actually be a more open system. Sure, you can't self host an MNO, but it's still a much larger step forward.