There’s a good chance that ordinal NFTs alone do not increase transaction fees. Well, they could increase fees, but not in the way you might think. After all, they benefit from the SegWit data discount, so theoretically a block full of digital artifacts would actually carry fewer fees than one filled entirely with ordinary Bitcoin transactions.
But if enough users start inscribing ordinal NFTs so that they seriously compete for blockspace with ordinary transactions, the users broadcasting ordinary transactions would need to increase their own fees for inclusion. In this case, miners would likely prioritize as many ordinary transactions as possible, because they have a higher fee per byte of data and they can fit more of them into a block, thus maximizing fees.
So if ordinal NFTs create transaction fee pressure, miners will likely optimize for higher fees by including as many ordinary, economic transactions as possible.
