There certainly are purists that will make a lot of noise about this fakery but then who of us don't cheat just a little. If we didn't there would be no need for digital cameras, cropping, color correcting, or the dozens of other capabilities most of us use in Photoshop. I don't plan to use this much but do find it fascinating.
The picture below is what I started with. It was taken last summer when in Scandinavia. The red fence really spoiled the image but I took the exposure anyway. But with generative fill... first I selected the area that contained the red fence and a perfectly acceptable fill was automatically created. Second I thought the right lower corner would look nice with some wild flowers... no problem. Finally I thought a few ducks on the path would help the make the picture more interesting and the composition more balanced. This all took only a few minutes.
If you consider this a photo illustration (not a straight photo) it is quite a nice image I think. What are your thoughts?