The problem is not that GIMP has a different UI to photoshop. That's not a problem. Premier and Final Cut Pro have different UIs, and while there's some friendly banter about which is better most people agree that either work.
The GIMP community has utterly failed to understand that the problem with their UI is not that it's different from one particular competitor, it's that it breaks all user expectations about how GUI software should behave. A simple copy/paste operation between layers requires googling before a new user is able to do it - and all to save utterly trivial amounts of RAM. That's not "just different", that's objectively terrible.
The GIMP community has utterly failed to understand that the problem with their UI is not that it's different from one particular competitor, it's that it breaks all user expectations about how GUI software should behave. A simple copy/paste operation between layers requires googling before a new user is able to do it - and all to save utterly trivial amounts of RAM. That's not "just different", that's objectively terrible.