My understanding is that musicals have the exact problem of being way too commerical and basically adaptations of already, mediocre, work. The difference is that the indie scene is even smaller due to the relative costs of creating musicals.
There's certainly a fairly steady diet of musicals/plays on Broadway/West End that are adapted from popular films. And, while many are well done, they also just feel utterly unnecessary in most cases. (There are exceptions--Network for example.)