Though Broadway, with its vanities and oddities, is in many ways an easy target, hitting satirical bull’s-eyes is hard. Expecting Alessandrini to be as consistently sharp and catchy as the best musicals he ransacks is unrealistic. Even if the music direction by Fred Barton is, as always, top-notch, the show’s staging is rudimentary, the pacing of its mere 90 minutes erratic and pocked with potholes. As such, it’s probably a good thing that last summer’s planned production of “Forbidden Broadway on Broadway” didn’t work out; the scruffy, sarcastic, bare-bones revues that this franchise is modeled on no longer have a home there.