I hope that someday GIMP will have major change just like Krita & Blender. The UI of GIMP have received many complains.
I want to support GIMP but, especially for fast, professional use, the UI makes it impossible. Their raw features are on par with anything I'd want to do in Photoshop, it's 100% a UI issue at this point. And I don't get why it's this hard for open source projects to realize that (the only notable exception I know is Firefox, which I love).
I have a feeling that in many ways it's just a lack of resources to move things faster.