I'm no political historian, but my understanding is that political regimes that have been called 'communism', are significantly removed from the system that Karl Marx envisaged. It seems that Marx recognised the problems where communist states exist in a world where other capitalist states have great power. States don't exist in isolation and my understanding is that the failure of the Soviet Union was, to a large part, attributable to the undermining influence of capitalist states.
Not that I'm advocating world communism. I'm to the right of such a position, but I do think that Marx's ideas have much to offer us, and, in the current situation are very helpful.