I suspect I might be a rare fan of the movie, but yes, it is very dated

. Tim Minchin did Judas recently in London; wish I'd got a chance to see. And
Chorus Line is currently in revival as well; only one I haven't seen yet of the recent West End runs (Wicked, Little Shop..., Chicago, Guys & Dolls, Kiss Me Kate et al).
Hope not derailing too much, but are there any 'bad' musicals people here love? I have a soft spot for
At Long Last Love, Lost Horizon and
Song of Norway 
. And adore Ken Russell's
The Boyfriend. Guess I just love musicals in their infinite variety.
Don't get me wrong, I love the movie
Jesus Christ Superstar. Ted Neeley, as Jesus was great, I loved him singing
Gethsemane (I Only Want to Say) and Carl Anderson's Judas is amazing. Yvonne Elliman was just as good as the two male leads. I pull the movie out and watch when I feel the buzz. But it might be time for an updating, I've always wondered what it'd be like without the surreal aspect of the Romans in Muscle shirts and holding machine guns. Or of full sets being used instead of ruins.
As for bad musicals that I like,
Grease 2 does have some catch songs,
Cool Rider; funny songs that might not have been meant to be funny
Whose That Guy, and songs that go back and forth between silly and decent
Girl for All Seasons/(Love Will) Turn Back the Hands of Time.
I love musicals too.