I agree - I'm not a fan of the (main show) entertainment on the cruises I've been on thus far. I go to most of the shows (mainly because my first 3 cruises were as a single - what else would I do?) but I don't really enjoy them - the exception was on the Jubilee when the band played big band music for dancing before one of the formal nights.
My problems with it are that it's cliched and too middle-of-the-road for me. The Broadway/Las Vegas revues are probably fine, but honestly I think Broadway and Las Vegas do a better job. How about actually staging a real, complete musical? I know, lots more work, effort, but it'd be nice to see. The magic shows/jugglers are enjoyable as is - don't think anything needs to be done here. As for singers/bands, why not have theme nights? Jazz/blues one night, pop/rock one night, country/bluegrass/folk one night, classical (well-known arias, segments of masses/requiems) one night. Basically, mount some more ambitious productions - less emphasis on the PRODUCTION actually and more emphasis on the PRODUCT. I'm sure that most passengers have a long enough attention span to sit through an entire concert vs hearing "highlights" of Broadway shows and standards.