You are still relying on sites to hold your item for you. Items don’t exist in a vacuum, having ownership over an NFT doesn’t suddenly mean things will just interoperate.

For example, if it’s a game item, you still rely on one or more games to honour your NFT that claims you own it, and to implement that item in the first place. If it’s an image, that image is still hosted somewhere (and even if it’s embedded into the NFT directly, those bits are given meaning externally).

An NFT is just a receipt claiming ownership, what that receipt allows you to do still relies on external services honouring that receipt.

NFTs only solve one small part of the puzzle and I’d argue it’s not even the most important one.