I hesitate to weigh in here because my knowledge is limited to US copyright law and I recognize we very fortunately have a global community. That said, this discussion appears to miss the distinction (in the US) between original works and derivative works. Someone who adds to an original work creates a derivative work; and they "own" the derivative portion. The derivative portion is, in fact, their own creation. That raises the question of what AI actually contributes.

Did the AI platform find an idea/concept and apply it to the user's image/? If so, US copyright law does not recognize concepts, only tangible manifestations of published works. Or did the AI platform merely copy an original image?