It is important to try and get the record straight on the legacies of marxism, and a figure like Plekhanov is not easily judged, but in the end the overall failure of marxism, dialectical/historical materialism is more than clear from the record. The whole backdrop to marxism is wrong and a larger perspective is needed to start over. Even the materialist critique of idealism is useless.
As against this much in the marxist corpus is useful and can be adopted into a new overall view: questions of class, exploitation, critical economics, etc…
As an example, marxists detest Kant (and Hegel) who carefully critiqued newtonian reductionism and much else and then want to replace all that with the most idiotic form of scientism. It is strange and unfortunate that marxism derailed completely.
Time to move on.