If your metaphor is correct, it remains correct even with a hash being stored on-chain. Frankly, most NFT critiques seem just as thinly thought through as yours.
The NFT is a ledger entry that says you own an edition of a piece of digital art. People coalesce around this believe, because the edition was released by whoever owns the actual copyright (ideally the artist).
The link is conceptually irrelevant. Cryptopunks never had one. As long as the community of collectors remembers and agrees on what each ledger entry represents, there is no problem. A hash can help with this, which is why almost all high-value fine art NFTs have one (in their IPFS-url). No, moxie could not be more wrong when he thinks IPFS should be enforced; the NFT never represents a set of bytes, it always represents an idea. The NFT may link to a 4K render of the artist's 3D scene, but it also represents the 8K render.
The first tweet will always be the first tweet, in the same way as the first transatlantic flight has no physical presence. If Jack sells the first tweet as an NFT, it is no requirement that Twitter stay online for ever. It is merely strongly preferred that someone will archive it so it doesn't disappear from our collective memory, but that need not be the job of the NFT. The job of the NFT is simply to record your ownership of the concept. And you need a blockchain for this, to give it the credible neutrality needed for it to be considered something equivalent to real ownership; you can't have it be at the mercy of a single entity.
If you think paying money for database entries is stupid now, imagine how stupdi it would be if they were in Google Art, a product that will shut down in 3 years, and where Google will delete all your art when your country attacks a neighbour.