There was no place for criticism of the entire system. Doing that would get you a very brief visit from the local KGB department, followed by your swift disappearance, and seeing your family again was not-guaranteed beyond that point. And yes, you could criticise individual members of the government, and you could point out corruption. But there were two problems with this approach - everybody(and I mean everybody) were corrupt one way or another, you had to bribe officials to get anything done, and it wasn't frowned upon, it was just how things were. And the other problem was, that that particular person whom you are reporting for corruption might be a close friend of a local communist party member, in which case, it's you who is going to Siberia, not them. So yes, theoretically you could criticise. But it was very unsafe to do so. Authors especially had to find new ways to write books which contained symbolic criticism of the government,but not too obvious, so it would go through the censorship.