Judy Garland had one of the great voices of the 20th century, but her battles with pills, alcohol, and men derailed her life. If you already knew that, there’s only one reason to see the new movie, “Judy,” and that’s Renee Zellweger’s lead performance.

Zellweger, who did all of her own singing, doesn’t quite have the voice Garland did, but at the time her scenes took place — the late 1960s — neither did Judy any longer. All of the musical numbers are fine, but the dramatic aspects of the movie drag as we see repeated shots of Garland too strung out to keep her off-stage life intact, and too beaten up by the years of hard living to get to her gigs on time.

There are some flashbacks with Darci Shaw wonderful as young Judy during the making of “The Wizard Of Oz,” when she was forbidden to eat lest she gain too much weight and forced to take uppers and downers that began her lifelong dependence on pharmaceuticals. There’s a lot of sympathy built up as teenage Judy is scolded by studio chief Louis B. Mayer, who seemed to feel that the way to encourage his star was to make her feel like crap all the time. It was mental child abuse.

I would have liked to see more of that and less of the older Judy’s battles to earn enough money to be able to keep custody of her two youngest children (Joe and Lorna, from her marriage to Sid Luft). But then we wouldn’t have had the opportunity to see Zellweger singing a few of Garland’s best-known songs. Or perhaps her story would have been better-suited to a mini-series a la “Fosse/Verdon,” with each chapter revealing more of Garland’s life and career. Too bad that’s already been done, in 2003, with Judy Davis as Garland in a performance easily as good as Zellweger’s, which negates the need for this version.

“Judy” does not include my favorite Garland song, “The Man That Got Away,” from the 1954 movie musical, “A Star Is Born.” However, I have another version for you to watch. We just saw Jessie Buckley in “Wild Rose,” a pretty good movie from earlier this year about a woman in Glasgow, Scotland, newly released from prison, who wants to get back to her passion, singing country music, while raising two small kids with the help of her mother (Julie Walters). Buckley — who has a supporting role in “Judy” playing Garland’s minder Rosalyn in London — has a helluva voice, which she proved over a decade ago on a British talent show, where she sang “The Man That Got Away” in the finals, only to finish second.

That performance is easily as good as anything Zellweger does in “Judy,” and the rest of the film doesn’t hold up as the great biographical drama it wants to be. I give “Judy” a 6 out of 10.