Hidde de Vries gathers some of the early thinking about CSS:
There is quite a bit of information on the web about how CSS was designed. Keeping it simple was a core principle. It continued to be — from the early days and the first implementations in the late nineties until current developments now.
The four main design principles listed are fascinating:
Authors can specify as much or little as they want
It is not a programming language by design
They are agnostic as to which medium they are used for
It is stream-based
So... did it?
I think lots has changed since the early nineties, but not really things that touch on how we apply CSS to structured markup.