how can you be a communist when communism never works?
I mean, if you want to go there, that's not technically true. As you would know if you knew how it actually worked.
What failed wasn’t actually communism as a whole, but the communist ideology used, in the form of Marxism-Leninism. Communism isn't the strawman of "everybody's equal" and it isn't something to simplify as such considering there's different ideologies such as anarchocommunism, Luxembourgian communism, the just mentioned marxist communism and leninist communism, and so on that haven't been attempted.
Ideologically-speaking, Marxism-Leninism has almost always failed for the same reasons, including state bureaucracy itself. Those who adhere to Marxist political ideology's goal is to use the state as a tool to get through relatively authoritarian socialism to communism.
Anywho, back on topic starting with an example of this issue in the USSR. What resulted from the revolutions wasn't socialism, let alone communism. Socialism is common ownership and democratic management of the means of production in a social group. The USSR certainly wasn't very democratic; that was an example of state bureaucracy taking over after "war communism". Yet, communism as a system is by definition stateless.
The entire “black book” of communism is thus being used to argue from a perspective which says that the system doesn't work, though its implementation hasn't.
(Furthermore, figures such as those who perished to Stalin's gulags before the war have been shown to be grossly inflated by experts who have extensively studied the Soviet Union.)
