I don't want to travel too far down this path. You have some jumble in what you wrote but I sorted it out and understand what you are (trying to) say. :-)
I did not refer to Greek tragedies and neither DEH nor WSS (or R&J) are Greek tragedies. The questions are whether a play can end in moral ambiguity and whether a play must convey moral purity as if it were a bible story. In my view, a play need not resolve itself into a neat package in which the audience is not called upon to wrestle with the meaning or consequences of what they have just seen.
And yes I acknowledge that sometimes in musical theatre songs are not especially in the service of the play.
Finally, a lot of modern tragedies have no hero with a tragic flaw because more often than not they are about a tragic result and perhaps a tragic misunderstanding. (There's a lot more, of course, but I don't think we need to address the remainder of Tragedies 101.