There's probably an argument that the difference between operetta and musical is that the former is written either before 1900 or not in English. Certainly the music of Carousel at least matches Lehar, and the whole experience is a great deal more enjoyable, and indeed profound, than The Magic Flute**. I've never heard a full recording, nor seen the film, but there were only two numbers I didn't recognise and I've been singing all of them for the past two days. The performances were uniformally excellent, the Opera North chorus and the Northern Philharmonia did their usual sterling stuff, and the dancers - let's just say I usually see the words "ballet" in an opera/musical and yawn, but the Louise's ballet section was enormously theatrical, helped I think by the young dancer's looking a realistic mid-teens. Though I'm glad that we didn't get the original hour and a half version, which - obviously - never made it to performance, even in 1945. It's on in Leeds for the rest of the week, then going to Salford, then the Barbican in London. Strongly recommended.
*I want to call him John Woodville, which is quite a different mental image.
**Admittedly Muppet Babies is probably more profound than The Magic Flute.