There's a question that isn't answered and that's why would users care about those details of the backend. In the end, a solution can be as technologically elegant as you want, but the thing it really needs to do is improve from the users' point of view. And I don't think it does.

For most people, a decentralized platform will usually be worse (speed, latency), and only very rarely better, than a centralized server. The "paying to access a database" will introduce a lot of issues both for users and developers, no matter how you implement it, for barely any user-facing improvement. And centralized processors appeared to make things easier, so you'd need a payment platform that is as least as easy and, also, that protects you against scams (AFAIK, you can't do too much if someone steals your crypto wallet or you forget the password).

So while I agree that web3 could provide identify + payments, it doesn't need to be technically elegant, but user-facing elegant.