That being said, I have had varying success using them on W10 with extracting the theme file with 7zip and installing the app themes individually. Worked sometimes with W10, but I don't know how well that will work with W11.
I've tried that, and you're right, it doesn't work with win11. The ONLY skin that has worked with for me is Oxidized. It would be nice if they could fix that on their end since we paid for them. I miss the winter Theme a lot, as well as the gloss grey, red, and green.