At its best, director Damien Chazelle’s latest movie, “Babylon,” is a starry and seductive “Great Gatsby”-esque tale of decadent excess and personal destruction — just swap the Hamptons for Hollywood.

What dogs the mostly enjoyable movie, though, is that it is yet another ode to Tinseltown, and can bear a striking resemblance to Quentin Tarantino’s “Once Upon a Time in Hollywood” and the Coen brothers’ “Hail, Caesar!” Sometimes it’s dazzling, sometimes it’s derivative.

Still, there are worse people to spend three hours with than Brad Pitt and Margot Robbie.

“Babylon” begins in the early 1920s, before “The Jazz Singer” revolutionized the movie business with the “talkies” in 1927. It’s set during the happy-go-lucky Pre-Code era ahead of censorship and morality rules sapping free-wheeling fun and laissez-faire acceptance from Hollywood.

Pitt, exuding the relaxed star power he always does, is a famous-but-fading silent film star named Jack Conrad, who is debonair but daft, wooden and a bit of a cad. Robbie is Nellie LaRoy, a New Jersey rebel with a harsh accent, who wants to make it big in the pictures. She seizes her opportunity at a raucous showbiz party thrown in a mansion at the film’s start. 

The bash is straight outta “Moulin Rouge,” only there are mountains of cocaine and this movie’s elephant is actually alive.

Chazelle clearly loves filming these complex, maze-like sequences packed with extras flooding in and out of lavishly appointed rooms, bawdily dancing and engaging in various family-unfriendly activities. Much of the movie is as frenzied and zippy as his Los Angeles freeway opening in “La La Land” (the director’s other ode to Hollywood). As in that musical, the music by Justin Hurwitz is once again percussion and brass heavy, and sometimes the beat is so pulsing you can’t hear the actors over it.

A similarly rousing scene occurs in a vast field where silent films are being shot. Nellie gets her big break dancing in on a saloon set, where she reveals she can cry on command. And Jack drags his drunken self into an epic battle in a period war film. The mania as multiple movies are being filmed before the sun goes down captures the Scotch tape-and-rubber-bands, no-HR, boozy scrappiness of the early days. 

That’s also when Manny (Diego Calva), a hanger-on of Jack’s, gets the attention of producers when he frantically goes on the hunt for a replacement camera.

We then watch Manny, who is madly in love with Nellie, rise through the ranks of the studio system to eventually become a powerful producer. Nellie’s star simultaneously explodes as depressed and aging Jack’s disintegrates. 

When the talkies arrive, Nellie tries out elocution lessons to sound proper and respectable (a nod to “Singin’ in the Rain,” which plays a big part in “Babylon,” but also Kaufman and Hart’s “Once in a Lifetime,” among other plays and movies). 

The film’s best scene by a mile shows Nellie on the set of her first movie with sound, trying to say lines while walking around. The crew just can’t get a good take in the can. Gaffers sneeze, doors slam, Nellie can’t find her mark under the mike. The vulgar screaming of an assistant director (P.J. Byrne) is unbelievably funny. The humor throughout is especially well-written by Chazelle.

Robbie is at her most addicting and outrageous in spitfire parts like Nellie. Here, she’s something of a Harley Quinn supplanted to sunny California, saying whatever she wants and acting in any way she pleases. A supernova.

Calva’s great skill, not to be underestimated, is his ability to look awestruck in the distance. Manny is our guide through this gluttonous world that teeters on the edge of a cliff and he reminds us of the moments of pure magic Hollywood has been responsible for.  

Jean Smart also shows up playing a Hedda Hopper-like gossip columnist named Elinore St. John. She delivers a poignant speech to Jack about how stars come and go, but live on forever on celluloid. Still the role, with a wonky accent that’s neither British nor mid-Atlantic doesn’t quite fit her.

Three-quarters of the way through, “Babylon” his a snag.

Chazelle becomes so obsessed with depicting the seedy underbelly of Hollywood in this satire that he goes over-the-top when Manny is forced into a desert, multi-level S&M sex dungeon by an overly creepy Tobey Maguire, complete with an alligator and sideshow performers. It’s a scene that could’ve been ripped from any trashy “American Horror Story” season. 

That blip leads into a sweet moment at the end, now in 1952, when we are confronted with the role that movies and cinematic innovation has played in our lives. It’s a lovely idea in a veritable ocean of too many ideas. The movie is a good 40 minutes too long and momentum ceases to build a while before it finally ends.

Still, when the director’s party is raging, you’ll wish you had an invite.