That seems a minor complaint about GIMP. It's should be easy to fix after the major changes get done. By that I mean full integration of GEGL and migration to GTK3. IMHO if these don't get done soon, GIMP will get replaced. It's been years since they "inadvertedly ported the core graphics code to GEGL".
You might say my priorities are wrong and GIMP is short on developers and I care about infrastructure more than something like gamma. But I'm moving to Wayland soon, and if GIMP has to run with GTK2 via XWayland I'm just not going to install it. OTOH I'm not a major user of it.
Krita [1], probably. They focus on painting nowadays because they don't want to be competing directly with GIMP, but it's a very capable photo editing tool. I use Krita for a lot of my photo stuff because it supports more than 8 bits per channel. Still, I think GIMP has enough developer attention, and GEGL is powerful and compelling enough, that GIMP won't get replaced any time soon.
You might say my priorities are wrong and GIMP is short on developers and I care about infrastructure more than something like gamma. But I'm moving to Wayland soon, and if GIMP has to run with GTK2 via XWayland I'm just not going to install it. OTOH I'm not a major user of it.