A better analogy would be giving your camera to a passerby and asking them to take your photo, with prompts about what you want in the background, lighting, etc. No matter how detailed your instructions, you won’t have a copyright on the photo.

I like this analogy a lot.

"Prompts" are actually used a lot in creative circles, whether for art or writing. But no matter how specific you are when you write a prompt for, say, r/WritingPrompts (and some of them are incredibly specific due to posters literally having an idea and hoping someone else will write it for them), the resulting story will never be copyrighted to you.