That's neither a positive nor a negative; dark, indigestible films don't do well at film festivals (this is known as the "Synecdoche, New York" problem).Nor at the box office, I think.
And it includes links to two parodies of Mamet doing Anne Frank: Village Voice and New York magazine. From the latter:
ANNE: But I want to be a writer!
PETER: And then you file your manuscript, and they cut the goddamn heart out of it. They want more of this, less of that. Add a hot girl, take out the power games, make it prettier. And Nazis. They always want Nazis. Such certainty they provide. I can’t stand it.