Which is the point of acting. You do research for the role and channel it thru yourself as an actor. No actor doing Chekhov knows what its like to be Russian landed gentry, or actors, or servants in the late 19th Early 20th Century. Research is required. There are no Jewish characters in Chekhov, or Catholics, or Lutherans, or Americans, or ... well you get the idea. That's why its 'acting'. Denzel Washington has no experience of what Romans were like in the time of Caesar - but he was very fine in that show. As was James Earl Jones as Grandpa Vandergelder few seasons back. Sam Gold proved a few seasons back that Othello doesnt have to be the only black character on stage in OTHELLO, by time shifting into a period when there would have been black soldiers in the army. It all made perfect sense and wasn't jarring in any way. Having African American actors play the two Jewish characters in THE LAST 5 YEARS opens a window for us to look at these characters in a different way, and pay attention to their jewishness very differently.