Transferring a work from one medium to another can be very painful. If you try to make a literal translation with minimal changes, the result is often clunky, dull, and unsatisfying. But if you try to make it less an adaptation than a fresh work written specifically for it's new home, then the purists will howl. This new "Bye Bye Birdie" movie tried to stay very close to the original play, and unfortunately it tried too hard. It has several really good individual scenes and musical numbers, but as a whole it spends a long time going to a lot of dull places on its way to a dead flat ending.
A stage play most always has human beings talking or singing or dancing or doing SOMETHING immediate and active, because no matter how fancy your set is, it doesn't change often and stage performers need to keep doing something interesting. Movies tell stories visually and so generally must change the viewpoint often to keep from being visually monotonous. This means having all sorts of scenes in all sorts of places, and you have to spend some time establishing these locations and following characters as they move around from one place to another; otherwise they will appear to instantly transport about. Good screenwriting can use these periods to seamlessly and quickly advance the story.
I think happened to this "Bye Bye Birdie" is that what might have been a quick paced play was slowed and fragmented so much by not adapting to cinematic necessity that any interest I had in the story and the characters was killed by its tediously viscous pace. It would have been better if they had simply filmed a stage performance of the play.
