The wage system, which Marx said was the foundation of capitalism, is also at the root of alienation. In German, alienate means to separate and the separation of the product from the producer is the essence of the wage system. This separation leads to the workers, the real producers of wealth, to be alienated from political power for political power, no matter what the mode of production is in civilised, class dominated society, is always organically connected with the ownership and control of the wealth which the producers create. Thus, the feeling of powerlessness which accompanies what we call alienation is founded on the wages system of slavery. Thus, the alienation from each other which we feel in our everyday lives and which manifests itself in various stabs in the back to our fellow workers as we compete in the labour market against each other in front the employing class, for a chance to sell our skills and time in order to make a living.
Marx wrote a profound critique of political-economy. I think he focussed so heavily upon it because he knew that the root of capitalism had to be destroyed before capitalist social relations could be surpassed and common ownership and democratic control of the social product of labour i.e. socialism, could be implemented.
Until the wage system is abolished, alienation will exist in spades. As long as the producers are alienated from control and common ownership of the product of their labour, they will remain powerless pawns in their rulers' political games.