Communism, as a philosophy, and what has actually been implemented in the real world, are very different things.
That is often claimed, but I'm not sure if that is really true. I do not think it is just a matter of bad luck that all real world attempts to implement communism ended in a horrible mess. Stuff like "Dictatorship of the proletariat" or "Class warfare" is right from Marx.
Communism does not ban the worship of God, god(s) or goddess(es), and the only place of proof is the communist manifesto, and I would have to cite the entire book to show it's not in there.
Communism as a philosophy contains far more than just the communist manifesto. All the other works of Marx, Engels, Lenin, Mao, Stalin, Trotsky, ....
You do not need to agree with them, but these works are still part of the philosophy of communism. There is not a single true version of Communism, but many different versions with different teachings and some of them are religions. What you are trying to do here, is the Communist version of the "True Christian" defense tactic. A Christian is still a Christian even if he does evil things, that are completely against your interpretation of what are a true Christian should do. And a Communist is still a Communist even if he, in your opinion, completely misunderstood Marx. Notice that I explicitly mention Marxism-Leninism and also Maoism in my last post. Sure, there is also a version of Communism that is just a economic system and nothing else. But Marxism-Leninism, Maoism and Stalinism are also versions of Communism and they are not just an economic system.
Atheist & Theism = religious systems
Atheism and Theism are not religious systems, but properties that can be part of religions and also non-religious world views.