Why do people focus on things that have never worked? Studying Marxism is analogous to studying astrology. It's the most failed economic system ever tried.
When you study Marxism you're studying an economic point of view, not a form of government. IIRC most of his work is observational and there's just not much to disagree with once you break essays down to a bullet-pointed outline.
The only thing you should be upset about with Marx is his prose.
Its more aching to theology, as the economic model is very simplified, assuming all constraints can be easily overcome - once you sparsed out the oversimplified sociological model. They have no concept for a limitation of resources, no concept for organizational complexity, no concept for investment pooling- beyond "the party of benevolent revolutionaries" controls all. Any toddler could come up with something more coherent..
The Labor Theory of Value is a basic component of Marxism and is demonstrably false.
The other tenet is looking at everything through the lens of class struggle. The modern incarnation of that is interpreting all of history in terms of race. Social mobility in free countries like the US shows that the class struggle theory is woefully inadequate.
Time would be better spent studying free markets, the law of supply and demand, etc.
The only thing you should be upset about with Marx is his prose.