There are heaps of Photoshop tutorials on YouTube, which wouldn't be necessary if what you said were true.
I used GIMP to do MS paint stuff years ago when I used it fairly regularly.
GIMP is always a whipping boy for UI design on forums like this and I think it is pretty unfair. It is a pretty good program comparatively. If you want to see bad UI design a much better example is something like Visual Studio. What a mess.