From Mary Gabriel’s fascinating biography of Karl and Jenny Marx, Love and Capital, describing an early meeting of the Communist Correspondence Committee, the first international socialist organization to which Marx belonged, in which Marx confronts Wilhelm Weitling, a utopian socialist:
Engels opened the meeting, attended by a handful of colleagues, saying it was necessary for those who wanted to transform labor to agree on how that might be done. In his memoirs Annenkov described Marx’s leonine head bent over a piece of paper, a pencil in his hand, while Engels spoke. But Marx couldn’t sit quietly for long. He demanded that Weitling, whom he accused of making “so much noise in Germany with your preaching,” explain his activities. Weitling offered vague ideas about acquainting workers with their plight and rallying them to communism and democracy, but Marx interrupted angrily. He said raising fantastic hopes on the part of the workers was mere dishonest sermonizing, which “assumes an inspired prophet on the one side and on the other only gaping asses.” It was not enough, he argued, for men to know that they were miserable, they had to understand why, and rousing the workers without offering them a clear plan or doctrine could lead only to failure. Weitling tried to defend himself, but Marx slammed his fist on the table so hard it shook the lamp and shouted, “Ignorance never yet helped anybody!” Everyone scattered. Marx was left angrily pacing the length of the room.
To me, this anecdote encapsulates the entirety of why Marxism has not achieved its goals.