Marxism, in the common understanding is a scientific theory of social reality
You’re talking about “the common understanding” which is ironic in the context of this discussion.
The fact that it is an economic reductionist theory of social reality does not mean it is physics.
I would agree with you if I shared your shallow understanding of the subject. Have you read anything rigorous about dialectic materialism or historical materialism?
Also do you think social reality isn’t a material reality? That is a rather odd position to have?