I think that Miller seeks to create an emotional drama whereby human frailty is on display for all to witness.  There is a universality in it because of this element.  However, I don't think that this stops Miller from offering a view of capitalism that shows the potential for destruction in capitalism, especially on the emotional front.  For Willy, his life is defined by material wealth, a condition of capitalism.  He seeks to be seen as something other than a "zero," reflecting a direct notion of how capitalism defines human beings.  Success is predicated upon wealth.  The more wealth one has, the greater of success is evident.  For capitalism to work, individuals must focus on this element and seek to remove all other notions of the good.  When Biff says that one of Willy's failures, representing his condition as a "low" man," was that he "did not know who he was," this is a reflection of the capitalist condition.  For those who lack material wealth are constantly driven to appropriate it.  They see themselves in this light only, a light of "other- directed."  In the process, capitalism is shown to remove any core of what it means to be "inner- directed."  For Miller, this becomes an indictment of capitalism in the modern setting.