"'Hello, Dolly' is close, but the waiters' gallop is merely a dance showcase and moves no story forward."
I beg to differ when it comes to the waiters' gallop. We're in this universe where people sing and dance when something major in their life is happening. Dolly is returning at long last, and that is SO HUGE they have to dance about it. It's not just preparing, it's a total celebration of this colossal figure. Without it, the actual song "Hello, Dolly!" would make no sense. I honestly wouldn't get the big deal. They could talk about how excited they are, but in a world where people sing about putting on their nicest clothes, it wouldn't be believable without a dance THAT BIG to celebrate it.
In terms of perfectly constructed plays, if we're opening that up, GLASS MENAGERIE is pretty excellent in terms of structure.
Some people paint, some people sew, I meddle.