I think that Miller is making a clear statement that the constant emphasis on wealth and monetary value which are intrinsic to a capitalist society can feature devastatingly brutal narratives. Willy's entire life is predicated upon being a "success," something that he defines in accordance to a capitalist conception of success. In this configuration, to not be "a zero" is the most important element. Willy's entire world is defined by wealth, a pursuit of the American Dream where money is the only currency that matters. Willy's drive to "make it big" is an indictment of the capitalist system, reflecting its demerits where wealth and money have more value than people. Willy might have been imperfect on his own merits, but Miller does make it clear that the true pain that exists in watching Willy's narrative is that he represents the biggest fear in a capitalist system. The demerits speak for themselves, as Willy recognizes that his life is worth a price, and that this can be deemed as successful. In a capitalist economy, everything has a price and this becomes one of its demerits. The commoditization of consciousness is the end result as one of the strongest criticisms in a capitalist configuration. In describing how Miller viewed an audience's reaction to the drama, one sees the fundamental demerits that Miller sees in a social order driven solely by capitalism:
[Audience members] were weeping because the central matrix of this play is ... what most people are up against in their lives.... they were seeing themselves, not because Willy is a salesman, but the situation in which he stood and to which he was reacting, and which was reacting against him, was probably the central situation of contemporary civilization. It is that we are struggling with forces that are far greater than we can handle, with no equipment to make anything mean anything.
In the end, one of the fundamental demerits of capitalism is that it compels individuals to participate in a system where success and failure are defined in the most brutal elements "with no equipment" to handle the brunt force of the latter, of which there are more in any capitalist configuration.