★★ ½

No, the liquid metal T-1000 isn’t in this sequel to the 1996 indie house hit about feckless junkie mates Renton (Ewan McGregor), Sick Boy (Jonny Lee Miller), Spud (Ewen Bremner), and their older, violent pal Begbie (Robert Carlyle), but it might have livened up the proceedings. It’s hard to top the tasting-blood exhilaration of the original Trainspotting’s opening scene, with Renton’s tennies frantically pounding the Edinburgh pavement to Iggy Pop’s “Lust for Life” as they’re being chased by the cops. Director Danny Boyle’s back for this one, and the sequel’s opening shot makes a witty parallel of Renton’s feet pounding a treadmill in a comfortable gym, a new metaphor for running and running and never getting anywhere – that is, until Renton collapses and shoots across the carpet in cardiac, not criminal, arrest.

The original movie made McGregor a star, and he’s still a devil charmer here, despite the mileage made apparent by intercut clips of him as a baby-faced, model-lean beginner. He was never a great actor, but a tremendously likeable one gifted with the Jimmy Stewart knack of getting an audience to forgive him anything. That’s fortunate, because Renton has a lot to be forgiven for, including betraying his comrades by absconding with the lion’s share of a drug deal in order, presumably, to make a new, junk-free life possible for himself. That worked for a while, but now, back home in Scotland recovering from his heart attack, he catches up with Spud, who has reformed but recently hit a low ebb, and Sick Boy, who has not reformed in the least. Sick Boy’s partnered with lissome Bulgarian prostitute Veronika (Anjela Nedyalkova) and the two of them are hatching a scheme to fund a superbrothel in his mum’s old pub. Is Renton in?

Of course he is, and there is one scene of a scheme so inspired it would be criminal for a critic to ruin the punchline, but the wit of that endeavor begs the question: If these characters are so infernally clever, why can’t they apply any of that derring-do or know-how to anything other than ruining their lives? Veronika puts them to shame. She is full of Millennial can-do spirit, and Renton and Sick Boy and all their Gen-X learned helplessness can’t ape her confidence, fueled as it is by growing up in a world where success is self-determined and painstakingly sustained one tweet at a time, not bestowed upon you by the powers-that-be. Their ’90s junkie angst was a panacea against that narrow Internet-less cultural window where disempowered young people were struck by lassitude and despair. But these grunge-era refugees are now Dinosaur Sr., and when Renton launches into an update of his “Choose life” monologue (this time lamenting Instagram, 9/11 deniers, revenge porn and designer handbags), it’s not a barbaric yawp, it’s a Yelp, a one-star review of how the world has grown up without them.

The original Trainspotting was a cautionary tale sugar-swathed in the delicious “heroin chic” delight of being young, decadent and still able to fit into 28-waist jeans. At 20 that behavior is Rimbaud romantic; at 40 it’s a nuisance. Why won’t filmmakers shrug off their “sequel-itis” and just let their iconic characters live their destinies without us anymore? Why must we revisit our heroes, whether it’s Renton or Han Solo, decades after their last noble exit, only to be disappointed by how little they’ve changed and how much we have? Maybe it’s the lack of Renton’s narration this time that lets us see what a flat and passive character he is in comparison to Sick Boy and Spud and Begbie. (Oh yes, Begbie returns too, and be warned: one extended scene between him and Spud, the thickest-brogued of the bunch, is so absolutely unintelligible they might as well be speaking Latvian, or Xhosa, with the word “shite” replacing the tongue clicks.) At one point a character complains that Renton is “a tourist in his own youth”, and that serves as a word to the wise for anyone considering watching this wan sequel instead of the still-stellar original. If you’re going to choose life, choose a movie with some life in it.