The public does. And if you make changes to it's only those changes made by humans of sufficient character to become copyrightable can be copyrighted and don't change the copyright of the underlying work.
If you make an image on midjourney and the make some changes the copyright status of the base image never changes. You don't and will never own copyright to it.
If you make an image on midjourney and the make some changes the copyright status of the base image never changes. You don't and will never own copyright to it.
Same thing with chatgpt.