Hm... If you ask me, its biggest flaw already is that they stick to death on the federal states organizing it. Literally each federal state does its own thing, comparing a single capacity between all of them is like a scientific discipline in itself.
And, on top of that, each federal state changes anything on its concept every few years - like either G12 or G13 (or allowing both), introducing conduct grades, redesigning how the diplomas are written in general and changing the lesson plans a lot.
Certain humanistic subjects even exist only in a couple of federal states - like, for example, the subject "Ethik". Somewhere else the same content is contained within "Philosophie".
I think, even between the school forms the lesson plans must be a bit different. At least this seemed to me to be the case for AWT (Arbeit-Wirtschaft-Technik). Gymnasium lesson plans didn't have a huge emphasis on crafts; you rather had to do with some more academic, economy-oriented stuff. This stuff somehow was unknown to same-year-olds who went to a Gesamtschule.
Later in the reorganized senior classes of the Abitur system, the subject was called only "Wirtschaft" with a direction according to that title.
In other words: Ein ziemliches Kuddelmuddel...