All the work in the workshop for CS:GO got a label that indicates that the works for CS:GO will not be accepted any more.
After the release of CS2, the skin models changed and the technology improved.
Now, if you want to make a skin for CS, you need to download new models and create a skin specifically for CS2.
By the way, if you have accepted skins for CS:GO – they need to be updated for CS2
More detailed:
This is an understandable situation. CS:GO is already in the past.