Oh wow, I did not expect to be disappointed by this movie, but I totally was! Yes, it's a very good looking movie, and OMG Johnny Depp's in it! Well guess what, they made a freaking musical with a bunch of bad singers!
Perhaps somebody can think of a better example, but for now, I'm going to blame the whole "it's okay to put amateur singers in musicals" mentality on Woody Allen's "Everyone Says I Love You." I mean I get what he was going for, he wanted to capture real people emoting through songs and to do away with overly polished & choreographed hamminess that musicals have become negatively associated with. I mean, we've all been to karaoke bars, where that one really drunk person really makes you feel that Def Leppard song, even though they've been off key the entire time. But guess what, that is the opposite effect of what you get when you put amateur singers with passable voices in a sound booth for a production like this. What you get are timid performances, with their voices lodged in the back of their throats. The Sondheim tunes/arrangements are perfectly lovely, but they never get a chance to pop. Instead they just wilt and lay limp, and the musical numbers become purely purfunctory and very very boring. And when the music doesn't come alive in a musical, then all the good will, perfect casting, and beautiful production design is just wasted.