To your point, I do understand and value the complexities involved in a UI designer’s work. Trust me, I have worked with UI designers in many projects as part of my job and I have also tried doing it myself in some of my side projects, and the results of the latter were horrible. So, I agree with your definition of it. But the purpose of my definition was not to belittle the work of a UI designer in any sense. It was more to give an idea of the difference in the work of three types of expertise mentioned above as briefly as possible, especially to someone who is new to the field and confused between all three. I hope this clarifies my intent and to that end, I have modified my statement to something I think, is less likely to be interpreted the way you did. Cheers !!