A novel idea for AI Generative fill

You have the ability to select the Subject - but you don't have the ability to select the background as the subject.  You can ONLY apply generative fill to the selected subject.

I want to simply change the background... it SHOULDN'T be brain surgery to do this

This is what I'm experiencing:

   Open a picture

   Select the desired item - this creates a mask of the item

   Now the system seems to figure out what tools can then be applied, and automatically disables them.   

   Not even the eyedropper works.

This is what I'd like to do

   Open a picture

   Select the desired item - this creates a mask of the item

   Tell generative fill to fill in the background

    Combine the generated background with the desired item

I've spent HOURS trying to get backgrounds changed on ONLY 2 pictures....so hate to say it but this AI stuff is crap...

Example prompt:  Fill the background with moon light

What is generated:  Moonlight and a groundscape...not even close