Being useful for sketching, drawing, and painting is actually a feature of generic editors like Photoshop or Affinity Photo. A lot of people use these software for painting with great success, and in some cases, even better than painting-dedicated softwares. There’s no evidence for the second part given it subjectivity and how the future isn’t always predictable. Some people like the OP of this thread used Krita for retouching with success. I also have retouched photos with Krita with success as well.
Of all of these, the only real argument is useful filters. Updates happens in both software, there are people that do want better selection tools, and some filters can be covered via g’mic for Krita, some of us like myself do plan to work on these (I’m working on the process of making mean filter to have guided selection tools for Krita). Opencl may or may not work, in my case, the last time I tried GIMP, it was far too slow, and I don’t desire to report the bug solely because I lost faith in GIMP for the absence of NDE and 8-bit restriction for years. Krita also support linear mode, so that’s not a real argument, and Krita has better color space support than GIMP now.
In other words, the “pure” photography part is what impact the end result mostly? That’s common knowledge for many people including myself, I just don’t know why to bring this up.