Death of a Salesman has liberal themes, but they're indirect and it can be viewed as a tragic portrayal of a man who stays the same as the world changes around him. It's still one of the best actors' plays of the 20th century -- Dustin Hoffman's best film performance.
I had the great good fortune to see Hoffman perform the role on Broadway, with John Malkovich as Biff. One of the best nights in the theater I have ever enjoyed.
Have you seen the one with DeForest Kelley? ;-)