I wonder if a project that replaces the "chrome" of GIMP with a different UX would be viable. Imagine a reworked menu / shortcut / dialog system that controls the unchanged core. Even better, imagine UI and UX to be live-tweakable, written in Python / Lua / Guile / you name it. That would make discovering better UI layouts and better UX flows absurdly easier.
(Yes, as an Emacs user, I want more software to be like Emacs.)
I have also worked as a “designer” in a real typography for some time and know a thing or two about the process (not fully, but count me as sort of an insider). And I can tell you that gimp is only “an artist’s impression” of a graphical toolbox, and that artist is heavily drunk. If you need something like gimp and paint.net/etc isn’t enough, you need photoshop. Cause we’re talking about serious pre-print color management, etc. Gimp is two parts: very poor home graphics editor and very poor industrial graphics manager.
Youtube thumbnails are paint.net 100%. I use that all the time for all my graphics, technical and creative, tried all others, and have no reason to switch, apart from OS requirements.