Yes that's what I mean by the manifesto and Marxism-leninism works great in theory but not in practice due to human nature. People are greedy, lazy and inept but also are ambitious and entrepreneurial. I think if Marx studied psychology a bit more he could've devised a more practical system. He certainly wasn't a dumb guy I don't agree with his politics but I can surely respect him for his accomplishments.
Marxism-leninism works great if in fact all humans were equal like Jon says and there weren't differences in tangible things like wealth, property, etc and intangible things like intellect, drive, etc. There's always going to be a group of people more intelligent/ambitious/lazy/greedy/wealthier than you hence humans are not equal. All you have to do is replace the adjective with any tangible or in tangible item.
But... Again when we tweak Marxism-leninism and the manifesto into the green book now we start seeing a more real life practical application of socialism. Gaddifs socialist revolution was essentially without casualty when he deposed long idris. Gaddafi did make the society more equal because the populace was given so much free or cheap stuff which basically eliminated poverty. However gaddafi and his cronies certainly lived better than the rest if the population. The same can be applied to any socialist state past or present - Stalin and the ussr, mao and china, the kims and no" etc etc. Basically they were not equal to the rest of the population.
In any political system there will always be inequality because the rulers and their cronies will always have it better than the general populous. Even if their income is identical their apartments are the same etc a ruler and his cronies will still have something that sets them apart from the rest whether its priority in a medical treatment sense, access to dom perignon during a reception, even nicer clothes to wear, and a less physically demanding job than sat a coal miner who will surely live shorter than say a politician who works in an office and will be given priority in treatment over one of the thousands of sick miners.
Short of eugenics, population control, censoring history and religion, total redistribution of wealth, erasing of borders and national identity, having the same infrastructure and economic opportunities everywhere there can't be total equality. You'd essentially have to reprogram the entire human race and unilaterally develop the world so all lands are at the same exact level. Until that happens a system like Marxism-leninism won't work as at the moment humans are not all equal in countless different ways.