The Soviet Union was built on slave labor.
Well that’s the basic idea of feudalism, isn’t it?
Communism is just a re-labeled version of that brand.
But at least the Feud required service from the manor lord: he had to go fight. The Communists couldn’t bring themselves to do even that: they also had conscription, and the only thing the Bolshevikii did was bring up the rear as Zampoliti.
All the downsides with no upside. Great deal, huh?