I'm reasonably fluent with modern tools (Photoshop, Sketch, Figma, etc.) and consider GIMP to be an incredible accomplishment. But as much as I'd like to use GIMP, I find it too painful to use even for simple tasks.
I wish someone would start a "sister" app leveraging the GIMP codebase as much as possible, but with an entirely different user experience and name, starting with Apple Preview-level MVP functionality and building from there.
Granted, I'm not a professional designer and the things I do are well suited for the GIMP. I usually manipulate bitmaps that will ultimately be displayed on a computer screen. This is not to say that all of the tools and workflow in the GIMP is good (the text tool, for instance, is horrible as far as I can tell). I'm just saying that there is a considerable bias when you start with one complex tool and evaluate another similarly complex tool that has a different UX.
The GIMP sucks for discoverability IMO, but I too find it comfortable because I'm familiar with it; and have found other apps crazy hard to pick up (Photoshop some years ago; Corel Draw clicked fine for me though).
I think graphics can be a bit of a grab-bag to some extent so logically connecting methods to put then in a menu hierarchy can be tricky.
Because it's not an imp.
Because it's wholly unrelated to the Gnome project.
In fact it predates GNOME by three or four years.
It's the GNU Image Manipulation Program, though most people find that to be too much of a mouthful; hence "GIMP".
How is Gimp less of a mouthful than Imp; would it not be worth the change.
I've used it for about 20 years, have tried to recommend it to people and always feel embarrassed to do so: similar to if they called it "shit-head". Not so bad as if you were recommending someone try Brainfuck.