This isn't true. There have been plenty of other applications (Corel, Paint Shop Pro, Fireworks, Krita etc) with their own workflows and keybindings that weren't confusing for users.

GIMP's UX is just bad. I loathe photoshop and desperately want to like GIMP, but each time I make the attempt the friction is too much and the workflows nonsensical. I used it a few weeks ago to place two images side by side in a larger canvas. It took half an hour in this mental little app to figure out how. I haven't have any issues with Inkscape and even Darktable ended up making sense. This is squarely a Gimp thing. Paraphrasing Kat Williams, "If people are calling you a crackhead for 20 years, you're smoking crack."