Crypto-currencies, for the most part, attempt to be fungible — all ethereum is the same and can be used for the same things. (There's a real argument to be made that BTC is not quite fungible). This is an important property for money to have. Shares in a company are fungible too, as are, say eggs (I can ask you for an egg today, I can give you another egg tomorrow, or I could give you the same one back if I haven't used it)
NFTs go in the exact opposite direction. Token are unique and not interchangeable. This models things like art, or real estate. If I lend you the Mona Lisa, you can't settle that loan by returning Guernica.
NFTs are really interesting in terms of the sort of applications you can build on top of them, but, as usual, the bro investor community around crypto is just milking the novelty factor for money.