Skins has gone from being the coolest to the least fashionable programme on television. After all, when you have to try that hard, it's already over.

For a while the creators made it look effortless. When Skins first appeared, it was the TV equivalent of one of its own characters: unfettered, impudent, wide-eyed with possibilities – a grown-up Grange Hill revelling in the shock of the new.

But, in four years and five series, it has aged it terribly. Suddenly, Skins no longer seems like something created by young people who really represent the youth. It now looks more like a TV executives' idea of what a drama for young people should be and what young people are like.

Skins has become the thing that it despised: middle-aged and cliched. The show's policy of replacing the entire cast every two series may be bold, but rather than keep it fresh, it has actually ensured that Skins has become stuck in a loop, like a trendy version of Groundhog Day: high jinks and alienation on the first day at college, make enemies, then make friends, then all take drugs and cop off together with ensuing emotional carnage and ostentatious lessons in growing up.

The three sets of friends have become exponentially less interesting. Tony, Sid, Anwar, and co from series one and two had to deal with issues that were actually intriguing and challenging: Lucy was caring for a mother with multiple sclerosis; Chris had lost a brother to a hereditary haemorrhage; Cassie's anorexia was tangible. Series three and four were carried virtually single-handedly by Jack O'Connell as the volatile Cook. This series the teens have endured: Facebook bullying, the perils of being a metalhead, and the prospect of inheriting the family farm. Pretty edgy eh ?

The characters are now mere Skins stereotypes, like faded photocopies. So we have the handsome, mysterious hero (Tony, Freddie and now the dreary Matty); The gorgeous but insecure superfox (Michelle/Effy/Mini); the socially inept geek/fool/virgin: Sid/JJ/Alo/Rich; the shy gay girl struggling with her sexuality: Emily/Franky; the irritating, absurd posh girl who the gang hang around with for no reason whatsoever: Pandora/Grace.

And then there's the show's mystifying preoccupation with unfunny cameos by comedians acting with all the subtlety of a pantomime – Chris Addison, for instance, currently seems to be doing an impression of how Alexander Armstrong would play his part.

Skins has been deposed by the newer, cooler kids in class – Misfits and Being Human, which are funnier, cleverer, sexier, wilder and much more imaginative. After all, how can a bunch of scruffy, feckless, students compete with two gangs of sex-crazed, blood-thirsty werewolves, vampires, ghosts, shapeshifters and other good-looking, wise-cracking young people with super powers such as mind-reading? Suddenly, the shock tactics in Skins (teenage girls experimenting with lesbianism, parties at their parents' house) look very tame indeed.

Virtually every scene is introduced with an achingly cool soundtrack – music in Skins is blatantly used to pad out each episode to a full hour. But this now is the best thing about Skins. The show is not so much a relevant, affecting drama but one long opportunity to use the Shazam app on your phone to find some new music to download.

• Jim Shelley is the TV Critic of The Mirror