RentBoy I completely disagree with like everything you just said.... I believe the opposite to almost every detail :)
First, though the tag "musical" does imply being sung and having the story told through music, there are many different types and styles of musicals and they certainly don't need to include dancing, a chorus, flashy costumes... ("people" don't expect that, though maybe tourists do).
Next, your examples of "The Chairs" and "Grey Gardens" show exactly why certain shows don't belong on Broadway! The Chairs with both it's original and revival production together played less than 3 months and though Grey Gardens played for longer, it flopped financially and had a 50/50 critic success, i didn't see it so I can't comment on it artistically, but I had no desire to see it and those that I know and respect who did found it quite boring and useless (with some good performances obviously).
You say that this show is told through music and though it could "be fleshed out and told in a conventional style, but then it wouldn't be half as interesting." The whole point and concept that makes a musical (any musical) somewhat believable is that it is a story and when a character becomes emotionally peaked or the story climaxes it breaks out into music as an extension of the character/story... a musical should not just be a story that has music to tell the show. I also haven't seen this show, but I have a feeling that this is one of the main issues. Why would an audience want to see 90 minutes of singing between two guys that don't emotionally need to be singing (if that makes any sense).
Finally, I LOVE when people say "Can this show survive on Broadway"!!

Yes there are many factors to it and no one ever knows, but like everything in theatre (from a performance, to directing, to writing) and even just in life.... there is a technique and process. I am not saying solely that a show's success is dependent on it's finances, but if a show closes after 1 performances (Glory Days) then no one will see it and it it won't be able to artistically succeed without an audience. Successful theatre is a magic partnering between all parties involved from artistic to creative to managing, and in my opinion, when the producers decided to use Broadway as its medium the overall success of the show failed and that is when the fate of this musical financially and artistically will fall.