There are just too many special-use-case tools to make a "good" UI. Learn it and forget about what it looks like, it's the only way you'll ever be happy.
No, Photoshop has never had a good UI (neither has Illustrator).
The problem is that people who use Photoshop on a regular basis have memorised the keyboard shortcuts and steps needed to complete tasks. The Photoshop way of doing things, no matter how clunky or unintuitive, is now the natural way of doing things for them (and their frame of reference when trying out another app).
It's no different to a lot of other software e.g. the programmer who won't consider any other editor unless it has the same task flow and keyboard shortcuts they've spent so long committing to memory.
This puts rival apps in a difficult position. Should they copy the same clunky, unintuitive way of doing things to attract users? Or forge a different path? In the case of Photoshop, copying the UI and task flow means users can also take advantage of the gargantuan volume of existing Photoshop books, tutorials and training available.
Illustrator is a pain, fine, whatever.
Photoshops UI is optimized for its workflows. I was able to learn Photoshop easily enough, I've been able to learn other image manipulation programs quickly, but despite having spent many hours in GIMP, I hate every minute of using it.
If I go "create new image", there isn't an option to create a new image that is the size of the image on my clipboard.
There is not a dedicated "interact with this selection" tool, like the arrow tool in PS, instead there is a tool that sometimes draws new boundaries, bit the rectangle select tool also moves newly pasted layers, which is a different action than the move tool, which is also confusing.
Pasting just sucks. Why is it a new floating layer that I then have to right click on and say "new layer", just create a new layer, not this annoying psuedo-layer thing.
Everytime I want to move something I have selected, I want to scream. I create a selection, so, move tool right? NO. The move tool lets me move layers I have made. Joy.
In fact after having spent a couple minutes on it, I still can't figure it out, but then again why GIMP is so damn confusing I have to figure things out every time I use it? Good programs are learned, GIMP is suffered through.
The way to move something that is selected is the same in literally every other image manipulation program ever made, but GIMP has to be different.
Hilariously enough, all other transforms on selections are super easy, just not translates.
Actually, you know what, I just looked it up.
To move the selected pixels, the user is supposed to control-alt-drag, then release control and alt, and keep dragging.
One of the most common interactions in an image manipulation program is hidden behind a double-meta with a click drag attached to it, and then a release of that double-meta?
That is jaw droppingly bad UI.
