People make this mistake because they think there is a "function" part to NFTs. It's a ledger, and you want to remember what media an entry refers to. You can do that by just keeping it in your community's collective memory, or you can use a hash of the file, or both.

People can then choose to value that ledger entry, or not.

Everything else, such as the ability of n app to figure out an image URL for the NFT, is just sugar on top.

NFT people will value a Bored Ape token whether the URL is valid or not - and they are entirely right to do so. The Cryptopunks don't even have a URL!