The relevance of Marxism to science is that it removes it from its imagined position of complete detachment and shows it as a part but a critically important part of economy and social development.
For some years I deserted religion in favour of Marxism. The republic of goodness seemed more attainable than the Kingdom of God.
What guides Marxism then is a different model of society and a different conception of the function of the knowledge that can be produced by society and acquired from it.
An excessive knowledge of Marxism is a sign of a misspent youth.