Had Hitler been able to carry on, the extraordinarily productive German economy would have faced collapse once the supply of slaves was used up. Of course by then, the war would have been over and it would have been time to transition to a sustainable peacetime economy.
In the case of China, parallels can be drawn between use of the rural population and Hitlers use of foreign workers.
interesting statement -- you are right, the CCP is no longer really communist, more a totalitarian oligarchy.