What about the Soviet system is more prone to corruption than, say, your standard Western Country? If you can answer specifically what you're concerned about, then we can answer why the Soviet System is better, or has had advancements since the USSR such as the concept of the Mass Line to account for weaknesses.

If you're unfamiliar with Marxism, I can recommend some good reading to understand it. It's incredibly easy to make up your own conclusions about Marxism if you are only aware of part of Marxism, which is a broad topic itself.