Given that 2013’s “Frozen” became the highest-grossing animated picture of all time, and spawned a hugely profitable Broadway show among myriad other ancillary sources of income, it’s understandable, though unfortunate, that Disney found it impossible, as the title of the movie’s once insanely ubiquitous hit song instructed, to let it go. Instead the company has come up with a sequel that suggests the salutary injunction of that lyric should have been followed: “Frozen II” is an unwieldy mixture of Broadway musical, animated adventure story, and message movie about not only the importance of family but the evils of imperialism.

“Frozen II” is set a few years after sisters Elsa (voiced by Idina Menzel) and Anna (Kristen Bell) were happily reunited in their kingdom of Arendelle, bringing along their pals, strapping Kristoff (Jonathan Groff), his reindeer Sven, and lovable snowman Olaf (Josh Gad).

But Elsa, now in control of her icy touch, is haunted by sounds no one else can hear—an ethereal voice singing a song. She’s convinced not only that it emanates from a mist-shrouded forest to the north called Ahtohallan, but that it’s related to her powers, and to a story that she and Anna were told as girls by their father Agnarr (Alfred Molina) who, with their mother Iduna (Evan Rachel Wood), have since died. That tale told of the princesses’ grandfather Runeard (Jeremy Sisto) trying to aid the people of the forest by building them a dam, but becoming the target of a magical attack there—resulting in long-standing hostility between the two realms.

Intent on finding out the truth, Elsa, Anna, Kristoff, Sven and Olaf are off to Ahtohallan, where they encounter the Northuldra, the native tribe who are their long-time enemies. What they discover, however, turns out to be something very different from what’s preserved in Arendelle’s history, and they wind up aiding the Northuldra to free their land from the curse of the mist that’s long enshrouded them, facing perils along the way—including some giant rock monsters that look like refugees from “The Neverending Story.”

In the course of their odyssey, of course, the troupe learn about themselves—the depths of the sisters’ commitment to one another grows even further—and those they encounter, particularly Yelana (Martha Plimpton), the leader of the Northuldra, and siblings Honeymaren (Rachel Matthews) and Ryder (Jason Ritter), younger members of the tribe. Kristoff ponders at length how to ask Anna to marry him, and Olaf wonders about how he can get to understand the world better.

The comic-relief snowman’s reflections are the basis for the movie’s best song, “When I Am Older,” which sounds very much like the Broadway show-stopper it’s clearly intended to be. “Frozen II” is, in fact, structured so much like a New York musical that one has to wonder whether it wasn’t first envisioned in those terms and then converted into a screenplay. Each of the principals gets a big number (almost all of them pretty generic, and certainly none with any likelihood of matching the popularity of “Let It Go”), and there are a few ensembles and chorus to pad things out. But the songs are separated by long stretches of conversation, much of it tediously expository, though room is left for a big, literally explosive finale.

It goes without saying, of course, that the movie has been given deluxe treatment from the Disney animation department: the visuals are ceaselessly spectacular. But however good-looking the film is, despite the fact that one of the heroines has special powers, it lacks any hint of genuine magic.