What are the weaknesses of the Marxist concept of society?

Classical Marxism was a product, in a sense, of the Industrial Revolution of the nineteenth century. Marx was astonished by the economic change that engulfed Europe, and horrified by the human costs of these developments. Marx thought that industrialization was creating a class of workers (the proletariat) who, increasingly alienated from the value of their labor and subjected to poor working conditions, would eventually rise up and overthrow the bourgeoisie, or the wealthy class that...

Classical Marxism was a product, in a sense, of the Industrial Revolution of the nineteenth century. Marx was astonished by the economic change that engulfed Europe, and horrified by the human costs of these developments. Marx thought that industrialization was creating a class of workers (the proletariat) who, increasingly alienated from the value of their labor and subjected to poor working conditions, would eventually rise up and overthrow the bourgeoisie, or the wealthy class that controlled the means of production. 

Of course, this hasn't happened yet, and this is perhaps the biggest weakness of Marxian concepts of society. Marx failed to anticipate many crucial changes. For one thing, he did not recognize the appeal of democratic or state socialism, and especially didn't think that capitalist states were capable of enacting the types of reforms that created welfare states in the late nineteenth and the first half of the twentieth century. He also imagined that the proletariat and the bourgeoisie would become monolithic, and failed to anticipate that the complexities in economic development would lead to more complex social relations (in short, not all working-class people would have the same interests, because some would make more money). 

Perhaps the biggest weakness of Marxism is theoretical. Marx understood the world and all of human relations in economic terms--the relationship of people to the means of production. Everything else he dismissed as "superstructural," simply reflections of economic realities. Many would argue that this is far too reductionist and simplistic. Such factors as race and religion, some say, transcend class and economic relations. Still, Marxism remains a powerful force in many academic fields, including sociology and history, and while few would describe themselves as "Marxists," his analysis of history and human relations is very influential.