The argument over the UI in GIMP and Photoshop is actually based on the kind of "false" premise that Photoshop has a "superior" UI.

It reminds of my first experience using macOS, as a long time Windows user. The first few months on macOS was a totally frustrating and negative experience for me - "What the ...? why does the ENTER key not open files or folders? Why is it going to 'rename' mode? Why doesn't double-clicking the title bar on a window maximise the window? Why are some windows maximised and others take their own custom width? Why is the Maximise button making apps full screen!?" - and so on.

The point is that I had become so familiar with the Windows UI, that every other OS UI suddenly seemed alien - "This is not how a UI should work on an OS". (This was also the reason that I hated Ubuntu's DE, as it tried to imitate the macOS UI I was then unfamiliar with). Familiarity means when you face a new UI, you have to spend effort to re-learn your way of thinking around a UI, which can be a frustrating experience (especially as you grow older). That effort / stress also unconsciously creates a negative impression in your mind about the UI. Both Apple and Microsoft know this and that is why they deliberately make their UI distinct and different from each other - whether it is Windows vs macOS or Windows Phone vs ios. Recently someone (a non-geek) asked me if they should buy a Macbook as they had an iPhone too. As they were a Windows user, I warned them that the macOS UI would be frustrating and to try macOS before committing to it. They did, and ultimately decided against it and chose to stick to Windows (buying a Surface Tablet).

As a former graphic designer, and an experienced Photoshop user, I only considered GIMP as a replacement when Adobe decided to make it a subscription. And just as with Windows to macOS, re-learning to use the GIMP UI was a frustrating experience because I was always thinking of "this is how it is done in Photoshop". Once you let go of that "familiarity", and are willing to actually test if the "GIMP way" is maybe better, it becomes a less frustrating experience. (All that said, while I have got used to using the GIMP tools the GIMP way, the overall GIMP layout does have a cluttered feeling and I do recommend installing Photo GIMP - it won't really make GIMP a Photoshop clone, but it will make it more "familiar" and thus easier to "re-learn" how to use it).