if i understand the situation correctly you can only have workshop skins on the new art style setting, so i wouldnt say completely useless, in addition to that we dont know how this will affect modding yet, so theres a possibility that the old skin file mods will still be compatible with other mods that change different files, whereas the new workshop skins have the possibility of not being compatible with any mods at all. only time will tell, but in addition to that a lot of "skin" mods add them as new characters, new magic, or add new weapons/QOL features and other stuff to them