I don't think it necessarily reflects bad on Mullally, or well, at least not in my opinion since I actually think it makes sense she didn't want to open with a show that was going to receive the same critical dismissal that YOUNG FRANKENSTEIN got and she cannot keep getting herself involved with that kind of show. She doesn't need to do stage, she does it because of her passion for the art form so why open a play that is clearly not headed the right direction? It also sounds that she had specific problems with the way he was portraying the character of the homophobic brother which implies she may have had issues with the way he approached the role and the way it might have come off on stage, it's a tricky character to play. And Joe Mantello is not completely off the hook since the Times does say that Mantello did have a "brusque" reaction to her pleads. Not to mention the fact that Mullally also seems to have a problem opening a Broadway show that she thought was likely to get trashed by critics when her mother is ill. Why bother?
And really, when was the last time Mantello got a good performance out of anyone? It sounds to me like Mullally did not want to hurt her reputation as a talented stage actress by appearing in yet another Joe Mantello fiasco after seeing the way he handled rehearsals and the actors. And something tells me the production wouldn't have been completely cancelled if there hadn't been more problems with the whole thing.
"Some people can thrive and bloom living life in a living room, that's perfect for some people of one hundred and five. But I at least gotta try, when I think of all the sights that I gotta see, all the places I gotta play, all the things that I gotta be at"