Well, hop in your time machine, as the Manifesto is quite a document for its time.
It is aimed at Europeans of the 1840s and 1850s, and even some of the intro's by Engels point out that the situation has changed, even by the 1890s.
I once did an awardwinning history paper on the topic the Marx's ideas as presented in the Manifesto were outdated before they could be implemented. Even by the time of his death, the situation had changed dramatically. That doesn't mean everything he said was worthless, but a great deal is best suited to its time, such as the positions on various political parties, most notably.
Other positions have already been implemented (various taxes), others outdated (the formation of agricultural armies), and others never touched ( the abolition of the family)
Sure Stalin probably had some mental problems, and killed many people, but ignoring him as part of Communist histroy is like ignoring certain parts of the Bible where the Israelites destroyed various other tribes, men, women and children. Don't follow him, but read him, to understand how a man could do what he did.
There is no such thing as "pure" communism, and hasn't been since the early days. Even after then, it metamorphosed in Fabianism, Marxism, and Leninism.
Read Lenin. He led the first successful communist revolution, and also the Bolsheviks for a long time. Important.
Didn't understand your last remark on China, and don't know how Cuba got a mention. Please explain.
Also, the reason no communists have answered your call to overthrow democarcy is that maybe they don't think it is time and are working on something themselves (involving aliens, bees, and two sexually frustrated FBI agents.)
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Whether you like it or not, history is on our side. We will bury you.
- N.S.Khrushchev