If everyone is buying NFTs because they believe the price is going to go up, and they tell themselves that the reason the price is going up is because NFTs are useful, but in reality NFTs are not, that is irrational. So it allows them to have monetary value while contributing nothing useful to the economy, and in fact causing people harm.

It is possible NFTs do have value in the sense of being good, but them being priced highly does not give us useful signal there.