Great question. Arthur Miller was born October 15, 1915. The play was produced in 1949. This context is central in understanding the power and meaning of the play. Post-war America had a new version of the American Dream, which suggested that America was entering a time of prosperity through materialism. And it was this materialism that would bring happiness.
The play, however, looks at the dark side of the American Dream. Miller pokes holes into the American Dream and tries to show the emptiness of it. A capitalistic material culture is a distortion of the true American Dream.
On the one hand Miller is challenging the dominant ideology of the time, but he is also part of another movement or growing ideology. There were thinkers, artists, and other intellectuals who viewed this ideology of materialism (or the new American Dream) as propaganda that stultified the individual. Also they saw the rise of communism and the dangers this possessed. So, if we look at what Miller did, he was very much a part of a group of intellectuals who were challenging the system.
By the late 1940s, when Miller wrote his play, Willy's version of the American Dream was no longer viable, if it ever had been. Willy believes that one gets ahead through selling and that one becomes a successful salesman not primarily through knowledge and hard work but through personality. He believes that being popular and likable are the most important traits driving success, and that success means making a lot of money while sitting in a hotel room in a bathrobe and slippers calling people on the phone. In other words, his goal is making easy money.
Willy fails in this goal. He never makes much money and he never has an easy time of it. He's not popular and very few people attend his funeral.
Miller's play calls into question the ideology, a prosperity gospel of sorts, that said one could get rich quickly simply through being personable. After World War II, expertise, knowledge, and education became the routes to success. Willy had deluded himself with the idea of a shortcut to riches.