I didn't say they were serious, I said Matilda isn't. Although to me Phantom is. It also depends on the context you use the word. It could be serious regarding the subject matter, but it also could be serious regrading its success, acclaim or prestige. By the latter standards even Hello Dolly could be considered a serious musical.
Now, Fela! was a serious musical... shame you hated it.
I think the answer to your question depends on whether you like flatbody pick-up trucks or spangled red thigh-high boots. And if you like both, bless you.
Words don't deserve that kind of malarkey. They're innocent, neutral, precise, standing for this, describing that, meaning the other, so if you look after them you can build bridges across incomprehension and chaos. But when they get their corners knocked off, they're no good anymore…I don't think writers are sacred, but words are. They deserve respect. If you get the right ones in the right order, you can nudge the world a little.
I haven't seen Kinky Boots but I've read about it & it sounds weird. And also I saw Hands @ the La Jolla playhouse and I say Hands on a Hardbody ALL THE WAY!!!! Would definitely recommend that one!