Well... There was never classical Marxist communism, though it was a propagandistic "ultimate goal". So called Socialism was sometimes effective and at some stages even nice and it worked good enough to survive almost 80 years but finally it collapsed and reasons of collapse were internal IMO. It was neither good nor bad. It just was.
Now in ex-Soviet countries left ideology is less popular than in Western Europe. Communist parties have some support from old people who feels nostalgia about the past. In fact such communist parties should be classified as conservative with some improper lefty rhetoric which has nothing to do with their actual politics.