In order to control the labor process and thus the extraction of 'surplus' value, investment and the division of profits, the capitalist organization of work becomes a major source of alienation. The sub-division of labor. For Marx, human beings become human beings by creative labor. In most other theories of alienation, dis-employment and the failure to do productive labor is reduced to psychological factors such as lazness, sloth, stupidity or failure to prepare oneself. Or to genes, race, gender or other physiological factor.
Capitalism separates workers from each other.
It reduces the structure of self to the private, self-serving individual and thus destroys community while it encourages both racism and gender conflict. Think about what happens to students as they enter the classroom of the authoritarian professor. These bright, lively, funny, and knowledgeable people become quiet, sullen, dull and too often, servile. Marx, in his sociology of knowledge, said that the ruling ideas of an age are the ideas of the ruling class. Much of the dispute between Mr. Buchanan and Mr. Forbes makes visible this oddity.