The inability of the marxist left to extricate itself from darwinism condemns the whole subject. Along with the pseudo-science of darwinism (cleary seen by Marx, at the start), we have the equally vexed zone of ‘historical materialism’ and the failures of theory there.
That is why we have constantly suggested we distinguish (neo-)communism from its marxist wrapper. Historically the two are distinct in any case. Why not just throw out marxism, except as historical inspiration and start over? All the real insights of Marx/Engels can be restated very simply without the trappings that have made the left a field of target practice for endless critics.
This subject is as controversial as any other on ethics, but taken as a classic expedition the Kantian take on ethics is unmatched as one of the great success/failures in the history of philosophy. It is a very dubious canon proposed by marxists, to eliminate free agency and ethics in the name of economism (denying they have done so). It is an approach doomed to failure.
A broad approach based on Kant wary of its own limits could have served the left better.