Lots of musicals keep things simple on a narrative front, and that’s okay. Like, Singin’ in the Rain is not a particularly complex movie narratively speaking, and there’s no problem with that, since it’s funny, heartwarming, and admirably complex on a technical front. The same goes for The Wizard of Oz, which is timeless but is also, ultimately, just about a young woman trekking through a fantastical land; a point A to point B kind of thing. But it’s the journey there that counts and makes the film a classic. For a more recent example, look at La La Land, which is just about two people falling in love and having that relationship challenged by their respective professional lives.