In my opinion, the reason why Communism continues to be so idealized is simple.
Because it appeals to the worst human trait, namely pride, and sets it up as an ideal to which everyone should aspire.
Why hubris? Because Communism, as indeed in all Marxism, is not about learning about the world, but about changing it. And by change it should be understood, not to use the existing rules and forces in reality so that they begin to help man, but literally to change the very rules and forces according to the author's vision of how it should be, how reality should be, because the current one is, according to the principles of Marxism, pernamentally flawed in its very form.
That is, simplifying the argument, communism derived from Marxism refers to the human desire to dominate the world in every element of it, the conceit that man can be equal to God and even surpass him in creating the world.
Communists believe that they can literally rewrite reality the way they want and force it to work the way they want a better world to look.
In my opinion, Marxism and by extension communism, which betrays many of the characteristics of religion, is nothing less than the most serious Christian heresy in the entire history of Christianity, because communists de facto do not so much disbelieve in God as they refuse to recognize him as someone higher than man and that man in the place of God would do everything better and the world would be a better place.
This is why it is so catchy and many somewhat support Marxism in its various forms, for even if they don't believe that a communist paradise can be built, communism gives them the opportunity to at least try to possess omnipotence without any limits.
This is why there is constant talk about the crimes of Nazism and the mistakes of communism, because these people believe that the idea that man can 100% control reality is right and must be pursued. And why it must be pursued is already different motives, but their true and common goal for all of them is total control of reality.
If the Communists got their hands on a machine capable of rewriting reality they would use it without hesitation to make reality the way they want it.