I don't see why Great Comet would have anything other than a positive "legacy," whatever that means, and will probably have a more lasting impact as a whole on Broadway then any of the other shows you mentioned. No one thinks TGC is a perfect show by any means, but it's almost definitely going to be remembered as a directorial masterpiece by Rachel Chavkin, and overall as a triumph in design elements by Mimi Lien, Bradley King, and Nicholas Pope (the set, lighting, and sound designers, respectively). Much like Rent opened the doors to a whole slew of popular musicals (most notably, In the Heights, Spring Awakening, and Next to Normal), I think ten (or hopefully maybe even less) years from now, The Great Comet is going to be the show people cite as the trailblazer for a new type of musical theatre, one that we can't really foresee now, but it'll happen.
I mean, most people's beef with TGC is that it's style and weirdness over substance, and while I don't agree, imagine what it's going to be like when a few years from now a show opens that undeniably has style and substance. And it'll be traced back to Comet, no doubt.
Updated On: 6/16/17 at 01:19 AM