I think having older actors play those roles works better today, as nowadays we don't look at a 30 year old woman as being past her prime and not marriageable. And somehow the idea of Blanche having gone over the edge mentally makes mores sense in an older, rather than younger woman.
I don't know why some people think Blair Underwood isn't "masculine" enough to play Stanley. Just because the man is well-groomed and has played slick roles, such as on L.A. Law, doesn't mean he can't play a working class man.
Although I like Anika, I wasn't thrilled with her Maggie the Cat, and see her more as Stella than Blanche.
While it would probably work better if Stanley, Blanche and Stella are all black, I don't see why some of the other characters couldn't be of other ethnicities. Isn't one of the poker players named Pablo? The neighbor woman who brings the grapes from the French Market? Maybe even Mitch, although I'd like to see a black Mitch.
I would have no problem with a black Stanley being called a "Pollack." Marlon Brando was not Polish and Jessica Tandy and Vivian Leigh were not Southern.
Actually, the Streetcar I'd really like to see is the one that appears in Almodovar's All About My Mother--with the characters Huma Rojo, Manuela and Mario.
Coach Bob knew it all along: you've got to get obsessed and stay obsessed. You have to keep passing the open windows. (John Irving, The Hotel New Hampshire)