The point is simple: Marx is a compelling theorist and has legitimate critiques of capitalism, and there are large groups of educated, intelligent, good people who feel like Marx has their back in areas capitalism turns its back on. If you write him off, you are oversimplifying and underestimating Marxism.
World War II is often credited with bringing the U.S. out of the Great Depression, which is twisted. Frederic Bastiat (my favorite) would call this the “broken window fallacy”, pointing out that destruction is not profit. A shoemaker who spends two francs repairing a broken window is back where he started, neutral, although the window repairman is grateful for the support. It would have been better if the shoemaker could have spent that money on new shoes, or anything that results in a net positive. If someone goes down the street throwing rocks through windows, is that good or bad for the economy? If someone invents an unbreakable window, is that good or bad for the economy? Is it economically beneficial to crank out ships that are just going to get sunk by submarines? People are dying by the millions, cities are being leveled, and your conclusion is this boosted the economy? Twisted.