SASS and LESS provide really nice language improvements, but they don't fix all the crap about box models and positioning and polyfills and byzantine precedence rules and the necessity for silly hacks like this. It's just too complicated and painful to make things look the way you want them to look, which is the point of CSS. I've gotten pretty good at it and I've come to care a lot about how it works (e.g. this little visualization is a really nice demonstration), but this state of affairs saddens me; I wish I could concentrate on other stuff, and not how to make a goddamn triangle.
(At some level of technical hair-splitting, this isn't per-se CSS's fault and is more general DOM crapiness, but that distinction is largely irrelevant. They're still problems I'm expected to solve with CSS.)