How is this a tragedy?

Willy Loman is a tragic figure. He cannot focus on what is going on in the present; he often lives in the past and he regrets days gone by. His children are a disappointment to him. he is not particularly in touch with reality, especially after the reader learns that earlier in his life Willy had had an affair (cheating on his wife) and that Biff discovered this affair by accident when he dropped by to see Willy. Ultimately, his flaws "do him in"; he dies and no one, except his family, even attends his funeral. In the end, he will be forgotten and will not have left the world a better place. This is truly tragic.