Communist systems are unable to fully capitalize on all of their resources. What all authoritarian systems do is decrease total efficiency so that they can concentrate on specific efforts. We can talk all day about the fact that Communist economics are bad, but there is a reason that Soviet tanks, SAM weapons, and rocket engines were absolutely stellar: it came at the cost of everyone else, including all other countries within their sphere of influence. China is exactly the same way, they've dominated the entire market in electronics manufacturing by parasitizing Free Economic Zones, and colonizing swaths of the rest of the world.

These countries were not able to be controlled by the left, and the western leftists were regarded with contempt by their Soviet & Maoist comrades. In fact, for western leftists, it's pretty clear that it was the soviet's holding the leash in that relationship, not the other way around.