Having used Gimp and Photoshop fairly extensively, I'd agree that Gimp works, and it has the features that Photoshop has (for the most part). However, there's quite a bit of user interface issues with Gimp that make somewhat simplistic activities rather irritating.
Gimp kind of has the Open Source issue where it has tons of features, yet there's a large wall of complexity, zillions of little fiddly knobs to tweak on almost every process, and the interface makes you feel like you need to, because they're all exposed immediately.
Photoshop (personal opinion) is better about having an initially functional feature, with relatively "what you expect" defaults, and then layers of fiddly knobs you can tweak if you "really" want to or need to for a project.
Every time I've used Photoshop the whole UI/UX changed. Buttons are moving around, getting renamed. Some functions are hidden in submenus of submenus, etc.
IMO Photoshop is just simpler because people are usually used to it. In reality Gimp always had a much more reliable UI
Gimp kind of has the Open Source issue where it has tons of features, yet there's a large wall of complexity, zillions of little fiddly knobs to tweak on almost every process, and the interface makes you feel like you need to, because they're all exposed immediately.
Photoshop (personal opinion) is better about having an initially functional feature, with relatively "what you expect" defaults, and then layers of fiddly knobs you can tweak if you "really" want to or need to for a project.