Also proof of ownership only works as long as people recognise that proof of ownership as valid

Yeah, that's one of the main issues. You'll still need to rely on traditional legal systems.

In the most generous interpretation, NFTs can help with that? A little? "Here's a hash of the document, here's a hash of the document with my signature on it, and here's that same hash on the blockchain, which can be independently verified."

The second main issue is that you can do most of that without any cryptocurrency shit! The only benefit is that it becomes harder to fake and easier to verify.

But the third main issue is that that's not even how it's being used! NFTs aren't storing hashes of some piece of art, it's storing a URL to a centralized platform. This URL can change (and absolutely will when the platform goes down.)

So, in even the most generous interpretation of NFTs, they have little value. And that little value is completely undermined by how they're used in practice.