Marx

Marx is not synonymous with socialism. At the time he wrote he was one of the many socialist writers. In his writings he made lots of conceptual mistakes; a big one was confusing ownership with power. In second-wave, smokestack industrial societies the integrators have the power. So his misguided idea of revolution's target opposition itself was misguided. See link,

Marx, in the mid-nineteenth century, thought that whoever owned the tools and technology—the "means of production"—would control society. He argued that, because work was interdependent, workers could disrupt production and seize the tools from their boses. Once they owned the tools, they would rule society

Yet history played a trick on him. For the very same inter-dependency gave even greater leverage to a new group— those who orchestrated or integrated the system. In the end it-was neither the owners nor the workers who came to power. In both capitalist and socialist nations, it was the integrators who rose to the top.<

Another huge mistake is in his theory of value.

Actually this one is worse than a mistake; his logic showed if he followed his argument until the end, it would mean revolution was not necessary. What did he do faced with the collapse of his theory? He fudged. This in my view is unforgiveable for any thinker. Steve Keen talks about this in this podcast.

(BTW: what kind of moron thinks machines do not add value to industrial production? This is key in today's inequality debate, and Toffler's waves, a recovered Marxist)

Whether or not there is revolution is beside the point. The truth of the matter is Marx's reasoning and path toward it was completely false. Today's Marx to many is a mascot; with the big beard, looking "philosophical", who is somehow related to the idea of a revolution. For people who want to pursue such route, and in this era of image making, his can be a useful. But anyone who wants to develop any global understanding of the world such as it is today, this particular route will be tough.

Related

Chomsky: There was no socialism in Russia, after 1918. The "revolutionists" called themselves socialists, the West liked they used that word, because now the right in the West could associate authoritarinism with socialism.