You should read up on Zcash, because it seems like you have a very limited understanding of what is actually possible with this kind of technology :(. Hell: Tor

You should read up on Zcash, because it seems like you have a very limited understanding of what is actually possible with this kind of technology :(. Hell: TornadoCash--which is based on similar mechanisms--apparently worked so well, despite being fully decentralized software running on an existing blockchain (Ethereum), that it is now sanctioned (which is honestly a bit strange as it isn't even a group of people: it is software) by the legacy system that refuses to allow people to have financial privacy (which is a travesty) :(. Also, as much as I despise MobileCoin for various reasons (and thereby haven't used either it or Signal), as far as I understand, not only do you "own your keys", but the UI is almost as easy to use as Apple Cash (or whatever the name is for the specific payment feature Apple provides where you have an account filled with money that you can send to people using iMessage).