“Heavy is the arm that wears its heart on its sleeve.” That’s the best way to sum up this overwritten, overlong, stunningly obvious treatise on gender equality, consumerism and existentialism, whose messages get beaten to death beginning early on and never let up, an exhausting experience, to be sure. Writer-director Greta Gerwig’s latest offering, co-written with collaborator Noah Baumbach, features a dreadful script that’s about as subtle as a young adult novel, drones on and on and on for about 30 minutes longer than it needs to be, becomes endlessly repetitive, and incorporates story threads that could have easily been scaled back or eliminated entirely (such as those with Will Ferrell and Michael Cera). What’s more, much of the dialogue is either stupefyingly juvenile or sounds more like “writing” than anything anyone would actually say (even for a fictional fantasy character), with attempts at humor that often fall woefully flat. And, to be honest, for all intents and purposes, the project comes across like a two-hour commercial for Mattel (even if the company manages to find ways to poke fun at itself). To its credit, “Barbie” does have a few strengths going for it, such as its superb production design, some genuinely clever humor (especially its opening pre-titles sequence and occasional asides), and fine performances by Margot Robbie and Ryan Gosling (who manage to make this material look better than it actually is), as well as a heartwarming appearance by Rhea Perlman. Beyond that, though, this is handily the most overrated, overhyped release of the summer movie season, one that I’ll easily forget before year’s end – and one that conclusively proves the power of marketing, no matter what the quality of the merchandise being promoted.