Plenty of cases make this not so certain: Warhol's Prince photo transofrmation (court ruled making a photographers image into clearly Warhol style was transformative enough), Blanch v Koons, Cariou vs Prince (copied photos, minor changes). If you dig through copyright cases on art, these many well be transformative enough. Plenty of other quite similar art has been ruled not infriging.

And one could also try a parody angle - make enough of these of famous art and find some angle about mocking or parodying that art, and again it may well pass copyright muster.

A court could simply rule that these images are clearly not the Mona Lisa, and, if taken as a style, could be ruled transformative, just like the above cases.

The fact is these are transformative, with a different style than the original.