[ It is a well operated machine, though decaying and renewing itself at the same time, hanging between ultimate victory and ultimate destruction forever, much like the Emperor himself, dead and alive, entombed on a Golden throne. ]

Yes, the Imperium is built around a very complex hierarchy. And indeed, you are correct. Governing the teeming mass of humanity is... taxing. Fortunately, I am charged with protecting it, not ruling it. It is best not to have Space Marines rule, as the Horus Heresy proved.