Noah Baumbach’s latest slice of New York life is a stinging GenX midlife meltdown performed with achingly recognizable pain by Ben Stiller (The Secret Life of Walter Mitty), while Naomi Watts (Insurgent) looks on with bemusement from the midst of her own crisis. Is middle-age the new adolescence? For Josh and Cornelia, their 40s are bringing teenlike tenor of uncertainty and confusion: scary physical changes are happening, and looking back to their younger years brings a comforting escape from reality. So when they meet 20something couple Jamie (Adam Driver: Tracks) and Darby (Amanda Seyfried: A Million Ways to Die in the West), they are energized by their enthusiasm for, seemingly, everything, as yet uncrushed by the disappointments of life. Baumbach (Frances Ha) is brilliant at balancing genuine affection for these characters and their foibles with just the right amount of exasperation, and at imbuing generational clash with bittersweet wit and pathos. Where the film falls down just a bit is in the plot, which revolves around documentary filmmaker Josh mentoring wannabe Jamie. It works in a big-picture way, as a kick in the pants to Josh, whose current project has been stalled for years because he is paralyzed by process and (perhaps subconsciously) by a fear of failure. But ironically, it’s Baumbach’s process — in setting up an ethical objection on Josh’s part to Jamie’s new film — that feels strained and ultimately small, even for a man (Josh) who is all about overthinking things. Still, the cast is uniformly fantastic, and in between its cracks the film offers a lot of melancholy wisdom (“What is the opposite of ‘the world is your oyster’?”) about living life and getting old gracefully.