A central payment system is absolutely not a tool of oppression. Case in point: don't like it? Don't use it. People are still free to not use it just like it even didn't exist. For everyone that chooses to, there is now an instant and free payment method. Where is the oppression?

In your hypothetical scenario of nazis taking the gov, lets assume there is no central database. Nazis would go: ok banks give me your databases or else. Banks gives databases because they care about money. There, now nazi have central database. And in this scenario you have deprived the people of enjoying a really nice service.

Where is the win here I don't see it. Let's not do good thing because, oh, in a doomsday scenario good thing might be bad. Like, shouldn't we channel efforts in ensuring doomsday never comes to reality in the first place? This way we all enjoy good life with ever improving services.