But now none of the open source software can compete with AI generative fill, AI denoising, and now AI rotation.
To a Linux user, yes. To a professional, it was always a cruel joke, it was never close, even a few years ago. It's like saying Notepad++ is a functional IDE, or Kdenlive is a functional replacement for DaVinci Resolve.
I cannot stress this enough: Actual professionals do not think GIMP is a viable replacement, in any way, and never have.
Some would say that GIMP, Inkscape, and Darktable aren't really competitive yet because they haven't had enough investment. If we invested in them enough, and managed them well, they could be like Blender.
GIMP has been in development since 1995. Photopea was initially released in 2013, has been solely developed by one person, and is a far-and-away better Photoshop competitor. The projects themselves are mismanaged. GIMP should (frankly) be abandoned and completely reset, in my opinion, as being a failed attempt at salvaging old code forever. Wisdom is knowing when to keep pushing - and when to give up.