Matt Cipolla’s review published on Letterboxd:
Reference an older work and you're cultured. Allude to it and you're inspired. Recontextualize it and you're a capital-C Creative type, and if you're Quentin Tarantino, you might not have to do much else. Get a trio of revered actors, coast on their charismas, and underwrite their characters. Take the most layered one—the one who encapsulates the soul of the film—and shove her into a corner so you can spend time with two guys that are much more tired. Focus on the period detail more than anything else and upend what appears to be a surprising maturity with selfish gags, and you've got yourself something great. Right? … Right?
As it happens, Once Upon a Time… in Hollywood is a self-pleasuring fantasy more than anything else. Closest to the front—but not the center—is Rick Dalton (Leonardo DiCaprio), an archetypal western star whose career is on the decline for the first time. His stuntman, Cliff Booth (Brad Pitt), also doubles as a driver for the alcoholic actor, and is known around town for apparently having murdered his wife, which the film treats as a shrug of a punch line. Rick is trying to reorient his career. Cliff drives around a lot. Add in the fact that Sharon Tate (Margot Robbie) and her husband live next to Rick, and you've hopefully got something to sink your teeth into.
But don't get too excited. Sharon's husband, of course, is Roman Polanski (Rafal Zawierucha). It's obvious that he's hot off Rosemary's Baby, but just in case these people's relationships and pasts weren't already clear enough, they all ride on the shoulders of Tarantino's many motifs. Underdeveloped and irregular motifs, that is. Expository dialogue, superimposed text, and narration from Kurt Russell sow the seeds that have already bloomed for half a century, and while lots of stuff is happening in 1969 Hollywood, little of it has much weight here.