The Soviets and the Mullahs have been very unsuccessful in selling to their own people. The mullahs exercise heavy control over Iranian media. They let a little steam out, but they also arrest and kill those who go too far. They can't entirely muzzle the press only because the public is attached to it. As with their use of democracy, their dream is the appearance of openness without the reality.
Indoctrination also includes the corruption of education.
The Nazis destroyed the finest university system in the world. The Soviet Union accomplished absolutely zero in 70 years of intellectual life outside the hard sciences. Moscow U. The tenth pillar is a parallel state-party apparatus. In democracies, political parties are wispishly insubstantial organizations by the standards of government or corporations. This is because real power is vested in open institutions of government that really wield it and are subject to the restraints imposed by democratic legitimacy.