Just a week ago i was thinking the same. Until i decided to create an NFT. I hope i can explain it well since im not from an English speaking country:
NFT (Non-Fungible-Token). As much as i understood is that an NFT is an Art Project digital or physically (so it can be more than just pictures). For example you‘ve a picture and then upload it as an NFT on a side (most used side is Opensea like the TWD did). After that your picture is irreplaceable since it got into a blockchain or something.
Im not shure yet how it works since i havent uploaded anything yet. But i guess its just like with Ebay. You upload your picture then theres an auction where people will offer you prices. The higher the price the higher the auction.
But people doesnt offer prices with money they. They offer digital money i think its called Ethereum. Its something like Bitcoin just different currency. But you can convert the Ethereum to real money or use it for investments in Cryptos.
The negative side of it: - You‘ve to pay fees for the upload - Just like every auction (it only lasts for a short time). I think its possible to let an auction stay for 7 days to a whole month or more im not quite shure. But that means its risky. - Why people hate it is because they dont understand it and because of that they feel annoyed by this. The other thing is it contains a lot of electricity to upload NFTs into a blockchain. Some people claim it destroys the environment. Pls to the experts dont blame me idk how it all works.
So at the end i would say i understand a few thinks im shure of but overall i cant tell if everything is right. Im still trying to gain information before i upload one. I feel like explaining it to someone else kinda helped me with my own understanding.
In case someone has more knowledge. Feel free to correct me im still looking for informations.