[metaphorhacker]

Engels famously compared Marx to Darwin in his eulogy. But Marx's problem was that he tried to predict too much into the future and was shown to be wrong in almost all of it - most notably the only communist revolutions happening only in agrarian states.

Darwin (and Wallace) only provided a model of natural selection that predicts pretty much nothing about the outcome, only about the process that will be involved and the general shape of the outcome.

So Darwin is now (rightly) seen as a great scientist and Marx (rightly) isn't seen as a great historian. But the general shape of the Marxian model is still useful to many people. Even if it's not very predictive in any useful way.