That simply is not true. Marx’s sociology and anthropological work has some value but the vast majority of Marx’s views on economics are no longer seen as useful, accurate or relevant. Bringing up Marx as a source us like bringing up Adam Smith, sure they wrote highly influential works but what was correct has been incorporated into the classical literature and what is incorrect, such as the labor theory of value, is taught as an example of previously held incorrect beliefs.
Very little of what Marx did is relevant to today’s economics because the focus is so incredibly different.