While I oppose Marxism and all its evils I do think Karl Marx did have a point in some ways and he did address some problems, workers were being underpaid and suffering in poverty despite doing an honest day's work but his solution to the problem wasn't the answer, my biggest criticism of Marxism is its extreme collectivist tennat if destroying the individual. People's individual freedom matters, letting people live their own life the way they want is what let's things act in favor of the people, collectivism unfortunately doesn't let one live one's own life the way one wants and allows a higher authority to tell the people how they can and can't live their lives. As Milton Friedman once said "A society that puts equality before freedom will get neither, a society that puts freedom before equality will get a high degree of both"
I don't think Marx would've listened to anyone who told him his ideas weren't the answer, his ideas were based on praxology, he basically insisted his ideas work without any evidence to prove him right.