With an August 2023 Broadway opening, “Back to the Future the Musical” played 597 performances, a much longer run than most new musicals.

I don’t understand why.

Nostalgia for the highly popular 1985 movie? Recalling the charming performances of Michael J. Fox and Christopher Lloyd? Tourists’ choice of a musical with a title of a movie they’ve loved? The rollicking hit songs from the film? Asking, Can an on-stage DeLorean fly?

From my seat, these are the reasons for the musical’s longevity — and its subsequent national tour.

It certainly wasn’t for the freshly written songs and a new interpretation of the movie. The score is largely forgettable, and the lyrics are functional at best. There’s little insight into character or story beyond what the dialogue already communicates.

The score illustrates how difficult musical-theater writing can be; songs must reveal character and advance story, not merely fill time between scenes. Those skills are not automatically acquired through success in film, television or popular music.

Notably, the original film’s screenwriter and musical contributors were the musical’s book writer, composer, and lyricist. The creative team brought film and pop-music credentials but, ummm, no experience writing Broadway musicals. There’s nothing new revealed about the story. Memorable moments come directly from the movie.

It’s not a unique occurrence. Look at “King Kong,” “Rocky,” and “Almost Famous.” And there’s no recognition of the staged “Dave.” Mediocre adaptations and no post-Broadway life.

Bottom line: The movie worked. Why is there a musical that adds nothing?

This stage version has new songs, visual effects, and stagecraft, but no new insights, themes or character dimensions.

“Back to the Future the Musical” played the Winter Garden Theatre, one of the larger houses, which helped generate strong grosses even when attendance lagged. The average ticket indicates substantial discounting, lottery tickets, group sales, and lower-priced mezzanine seats. Despite its lengthy run, there was no return of its capitalization to investors.

We also need to consider the performances. The Eccles Theatre’s earnest cast sings strongly and dances with enthusiasm. David Josefsberg as Doc Brown and Lucas Hallauer as Marty McFly work to bring energy to their roles, but the script rarely allows either character to become more than a faint reproduction of the film originals. And they are directed too cartoon-y. But let’s remember they are saddled with a threadbare script and unmemorable songs.

The stage adaptation of the “Back to the Future” franchise is an expensive, capably crafted theme-park attraction. Artistic ambitions are surprisingly modest. Perhaps Broadway’s next adaptation will be “Knight Rider” — with Kitt, the talkative Trans Am speedster.

► Through June 14; tickets at saltlakecountyarts.org or 801-355-2787