Disclaimer: it's not that I'm denigrating the devs, making a program like gimp is super fucking hard and as a lousy programmer I could never be able to make it better. Ideally, it would need some talented designers to develop a more usable UI.
I see comparisons to photopea, but that's a UI clone of Photoshop and that is not really wanted. It also didn't come with technical debt from the 90s