I myself started my career as a web designer. I'm well versed in Photoshop, illustrator, InDesign, Lightroom, and premiere. Part of what makes those tools good is their fairly consistent UI choices and easy to remember shortcut keys, many of which feel intuitive and based on something.

Gimp definitely lacks some features, but I'd be happy to use it if it had a UI that didn't break my brain. I do not think you're being super fair about your assessment. Every time I've needed it for anything, assuming I had the time and patience, I've been able to do what I needed to in terms of editing with layers, applying effects, etc. But it was always fairly uncomfortable. So yeah I don't think it's an objective fact that no one would ever use it because it's the worst software ever.