Rosa Luxemburg, the murdered German socialist/communist has seen many of the shortcomings of the Lenin/Stalin type of Marxism early. In "The Russian revolution" she did write in 1918:

Freedom only for the supporters of the government, only for the members of one party -- however numerous they may be -- is no freedom at all. Freedom is always and exclusively freedom for the one who thinks differently....
Without general elections, without unrestricted freedom of press and assembly, without a free struggle of opinion, life dies out in every public institution, becomes a mere semblance of life, in which only the bureaucracy remains as the active element. Public life gradually falls asleep, a few dozen party leaders of inexhaustible energy and boundless experience direct and rule. Among them, in reality only a dozen outstanding heads do the leading and an elite of the working class is invited from time to time to meetings where they are to applaud the speeches of the leaders, and to approve proposed resolutions unanimously -- at bottom, then, a clique affair -- a dictatorship, to be sure, not the dictatorship of the proletariat but only the dictatorship of a handful of politicians, that is a dictatorship in the bourgeois sense, in the sense of the rule of the Jacobins...such conditions must inevitably cause a brutalization of public life

No, that is not written in hindsight, it was written in foresight. One may dream for a moment what if she had not been murdered in 1919.... But then the reality check comes in and says. Well, then she would have been murdered in 1938/39. Though I'm not sure whether in a German KZ or in Moscow.

Wolfgang