abstruse
[A]трудный для понимания; неясный; малопонятный; заумный; глубокий; глубокомысленный

It need not, after all, be so abstruse, or so deeply suspect.
There were so many books and periodicals to be read, so many abstruse thoughts to be thought.
Maths is a mix of abstruse theory and detailed calculations.
So occupied with abstruse ideas, that he is incapable of coping with every day activities.
Admittedly not all of the technicalities of the system are abstruse.