I understand your frustration. I also had it and sometimes I experience it still - depending on what I actually want to accomplish with MODx.
The problem, however, is, that
the path simply does not exist.
Each and every user will have to find his own individual path, since the fields and grades of previous knowledge and experience are all different. And so are the different requirements and needs for using MODx at all.
Compared to other CMS which provide a similar functionality (and this is the only comparision which I find is
fair), MODx is relatively easy to check out. Later on, when you feel the need to modify it (like writing your own snippets and the like), it gets more difficult. But in that MODx does not differ from other CMS.
At the end it’s the same thing with every new software or system you’re trying to master:
you need patience, the will to try things out instead of looking for a premade doc.
(Or engage a teacher..)
BTW: what is "server side CSS"? Never heard of that before, seems I’m more newbie than I thought...