Anna Kendrick is definitely slumming it (and slumming it it hard, yo) in this "romantic", "improv-heavy", "vacation" "comedy". But this isn't the first time she's done this -- cough*'Rapture Palooza'*cough.
Zac Efron and Adam Devine, however, seem right at home.
This is the type of dumb, PG13/14A comedy that doesn't have the freedom to be outright raunchy, so it forever skirts around adult situations, and just comes off seeming prudish. For example, the bride-to-be (Sugar Lyn Beard, who at times manages to steal the show) receives an unexpected "happy-ending" massage from 'Silicon Valley's Kumail Nanjiani that blows her mind, but it turns out the cause of her ecstasy is actually a series of oddly non-sexual moves, like a bum-on-bum oil rub. And then they make sure to mention at least twice that this was strictly a no-penetration massage. It's like they wrote the scene, ran it by the ratings board, and they just kept editing it and resubmitting it until they got the rating they wanted.
But wait. You know how a comedy can often succeed by leveraging the merits of warm, interesting characters that we grow to really care about (see: 'Forgetting Sarah Marshall', 'I Love You, Man', or 'Bridesmaids')? Yeah, this movie doesn't do that either.