I don't really hate NFTs but I'm very critical to (a) the way models of digital scarcity is introduced to digital artist by the blockchain (maximalist) tribes effectively making the whole thing very similar to pyramid schemes as you suggested, (b) carbon emission footprint of Proof of Work.
But to your question, I suppose any work in digital media which is fungible could be reluctantly considered as "polar opposite of an NFT". One could even do better than that and release the artworks under an open license like CC.
Oh that's a fantastic idea, I need to read up more on how an open license could apply to a physical artwork. If anyone has any further reading suggestions on that let me know.
First thought is maybe drawings / paintings / collages that are optimized for universal 8x11 printing where there is no original available and all copies are equal. Or maybe the same thing for a high-quality / printable 3D scan of a sculpture?
But to your question, I suppose any work in digital media which is fungible could be reluctantly considered as "polar opposite of an NFT". One could even do better than that and release the artworks under an open license like CC.