Same here. Designers might be able to put a finer point on it, but the aesthetics of KDE are just wrong to me. Every toolbar is an explosion of ambiguous icons, the spacing between text, icons, menus, and all of its other interface components seems off, slapped together and amateurish. Dolphin, Konqueror and Kontact are among the worst offenders. And there's also bizarre method for configuring the dock, and the whole plasma thing I just do not get.
I get wooed every so often to try it again, usually on the heels of a new release. Then after a couple weeks of *really* trying, *really* wanting to like it, I abandon it. The same is that QT apps can be *really* beautiful and awesome (eg. QT Creator) - but KDE apps just aren't.
And aesthetic appeal is really important to me... the environment I work in all day has to be visually appealing as well as functional. No amount of theme and style tweaking seems to get me to a visually appealing place in KDE. And this has been a consistent problem for me as far back as the KDE 2 era and onward (never ran KDE 1).