Marx was important. He explained capitalism in a way nobody had yet, and his ideas were an important tool for subsequent economists and thinkers to develop a better understanding, and build better models. Most take the mention of Marx as a grand ideological position. I don't. His ideas simply get added to the mosaic of economic intelligence through the centuries, and it gives us all a richer understanding. Things as old as that, preserved through writing (this can include music) don't survive at large in the global consciousness if they have no value.