You've bundled several ideas into this one post under an idea
if you haven’t post processed the image, it isn’t good enoughI can't speak for everyone, but when I think of
post processing, I have zero conception of replacing image elements, not skies, not flowers, not people's faces, etc.
First, I'm shooting in RAW, so by definition: I shooting for the specific purpose of editing the image via post processing. As a RAW shooter, I'm expecting to perform processing that is typical to all digital images (sometimes more, sometimes less): cropping for composition, leveling the horizon, sharpening, adjustment to the white balance, adjustments to the blacks and whites, adjustments to overall contrast, overall saturation and overall exposure.
Once you go beyond my own typical adjustments identified above, the processing work depends on the specific of the image and the vision of the individual photographer. If someone thinks a new sky is needed, good for them. I'd just delete the image if that level of effort was needed to bring one of my images to "successful". That's my own personal approach, which has no bearing on what others desire to do to their images. Although I seek to avoid complex edits best performed in layers, I do adjust the Luminance, Saturation and Hue of individual colors as well as clone away minor distraction in an image, where these improve the content of the image.
Regarding subscription vs purchase approaches to software, you seem to be unaware of how digital editing software companies operate as ongoing business concerns. Only this morning was there another post on a regular UHH topic, to paraphrase: I bought a new camera but my old software cannot edit RAW files from this camera. link >
https://www.uglyhedgehog.com/t-590077-1.htmlIf you only shoot JPEG and keep the lens profiles up to date within your camera, you likely can purchase a powerful standalone software package and maybe not require any new purchases, ever. A tool that accomplishes the typical edits, identified above, would be all that is needed, as least for the basics of my editing approach. Most any software priced in the $60 to $120 range will address these needs. And again, if you keep to JPEGs, you'd be well prepared for your digital editing needs for the immediate future, and possibly "forever" if you can migrate the software to new machines and OS versions.
But, when you change your camera model, replacing and / or add new models or vendors,
and you shoot in RAW, now you're presented with the fact that all of these software vendors are ongoing for-profit businesses. They each offer their own value proposition you're free to evaluate, typical for 30-days free of charge. If you think they should support and update their software for free for new cameras models into the unlimited future, based on your 1-time purchase payment, alas it doesn't work that way. Certainly not for $120. That 1-time payment approach would route you toward JPEG as described above, a perfectly valid and widely followed approach, but with the limitation you probably can't replace the skies and flowers and such.