can these be held and traded in a verifiable way?

Bold statement.

I would argue that just because something that could work doesn’t mean it is the best fit for the job for one reason or another.

We have multiple programming languages, database, filesystem, media formats etc…etc… Those also generally perform the same thing but some do certain things better and you pick whatever one best fits your needs.

why can block chain and go both existing and fit whatever role best fits them?

Not saying block chain / NFTs are the answer to ownership tracking just saying we shouldn’t write them off just because something else might work.