Well, the october revolution, even if it was a coup, was a coup against mostly other marxists (actually, the mensheviks were more orthodox).
I think there are two dimensions in which marxism, whatever your politics, will never be useless. First, a lot of it is a body of work authored by people in the midst of extremely bitter social struggles, civil wars, and revolutions. So you tend to get a pretty clear idea of how these things work, from the inside. Second, I think Marx is just a phenomenally clever and insightful thinker. I'm not particularly wedded to the economics (actually, neither was Lenin), but his thoughts on how economic and physical forces shape us as political actors are really good.
I think there are two dimensions in which marxism, whatever your politics, will never be useless. First, a lot of it is a body of work authored by people in the midst of extremely bitter social struggles, civil wars, and revolutions. So you tend to get a pretty clear idea of how these things work, from the inside. Second, I think Marx is just a phenomenally clever and insightful thinker. I'm not particularly wedded to the economics (actually, neither was Lenin), but his thoughts on how economic and physical forces shape us as political actors are really good.