I don't disagree with anything you're saying, all good points that I'm sure went into deciding to market it this way. And above all the art needs to help it sell tickets... the "Pulitzer Prize Winning" would sell the ticket to me no matter what the artwork looked like, and I'll never quite get why that wouldn't put it on everyone's must-see list, but that's me.
The one thing i disagree with is that Broadway is basic in this sense. Not sure where you're drawing that from. A lot of incredible poster art that isn't basic has come from broadway musicals. Maybe some of the ones I hold in highest esteem didn't help the shows sell tickets as much as other imagery would have, it's hard to know... again, I am not a typical theatergoer I guess, in terms of marketing to sell out a broadway run. But... at the same time, Broadway runs on passionate "insiders" like myself AND tourists.
Maybe this show is lucky because it already won a "must-see" making prize before arriving on Broadway... its artwork doesn't have to intrigue buyers like me anymore.