But the art itself is not scarce. In the physical realm, it's like a painting that can exactly replicate itself. The certificate of authenticity doesn't, though, and is the scarce component.

I think it's reasonable for someone to ask "if the duplicates are always exactly the same, what is the value of a certificate of authenticity? It would be drastically harder to forge a fake than it is to hit the button to make an exact copy".

It shifts the entirety of the value away from the art. The art itself is worthless. Anyone that wants a copy of the art can do so with a Google search. You have a scarce digital token proving that you are the rightful owner of a worthless piece of art.

That's why I don't see it working.