Doctor Who: has age withered this Time Lord?

I couldn't make it to Cardiff this week for the press launch for the new series of Doctor Who, but then, although mildly intrigued, I'm in no desperate hurry to make the acquaintance of the Doctor's latest incarnation. With his long, ascetic face, rather like Mervyn Peake's sketches of Steerpike in his Gormenghast novels, the 27-year-old Matt Smith has all the makings of an interesting Time Lord. And, after all, this revived version of the venerable BBC1 classic, with both David Tennant and Christopher Eccleston, has a good track record with its principal casting. I can well imagine that he will continue the vein of English (even the West Lothian-born Tennant spoke with an English accent) eccentricity that has permeated the show since its inception. However, on the whole, I increasingly can't be bothered with Doctor Who.

The energy and enthusiasm that Russell T Davies has injected into the dormant franchise since 2005 has won nothing but praise, awards and a large following of dedicated fans, and I count myself among the initial admirers – not least in resisting what you might call a glossy Americanisation of the property, and in retaining the show's essential, and very British, spirit. See the 1996 television movie, with Paul McGann's Doctor, to see how it could have been modernised, but happily wasn't. However, I'm no longer so sure that it's the unalloyed triumph that an increasingly self- congratulatory BBC would lead us to believe.

For while Davies has done well to regenerate the programme's left-field sense of humour – a spirited larkiness that has been there at least since Tom Baker inhabited the Tardis – it is tending to overpower everything else these days. The banter is becoming a tad remorseless, if you ask me, and is not being balanced out by the fear. Where is the tension and terror that's being undercut by all this insouciance and whimsy? Does anybody watch Doctor Who any more from behind the sofa, a de rigueur viewing position in my childhood?

All too often, this current incarnation seems to rely for excitement on that most tedious of dramatic devices – the chase – and every time he gets cornered, the Doctor pulls out his sonic screwdriver. Our eponymous hero should be able to get himself out of scrapes with the power of his intellect, not just with this magic wand. How is this sonic screwdriver supposed to work, anyway? And as for that so-called "psychic paper", in which people's thoughts can be transmitted to a credit card-sized screen – Steve Jobs, eat your heart out, but don't expect it on the high street in any millennium soon.

There is a distinction in science fiction between "hard sci-fi", with its rigorous attention to scientific detail, and "soft sci-fi", with its more social or philosophical concerns, but Doctor Who must be in a squishy class of its own. I don't know enough science to call it "bad science", but even with my humanities background it looks supremely dodgy. Rather like the new breeds of alien, in fact. The old ones, such as the Daleks and Cybermen, are great, because essentially they are Nazis. The new ones, such as the Slitheen (sort of malign, obese versions of Spielberg's ET), the Ood (take a close look at the head of your prawn, next time you barbecue one), and the Hath (half-human, half-fish creatures), look like guests at a Monsters, Inc fancy-dress party. If this is the best that evolution can come up with, then Darwinism needs a radical rethink.

Mind you, forget the horror; these days, Doctor Who is almost a romcom. Queer as Folk creator Russell T Davies has never been afraid of confronting taboos – but a romance between the Doctor, a 900-odd-year-old man, and his assistant, a teenage shop girl? To put it another way, Christopher Eccleston is old enough to be Billie Piper's father, and while I can see that paternalism doesn't appeal to today's younger generation, the earlier programmes would never have entertained an emotional/sexual attachment between the Doctor and his assistants.

But these reservations are almost beside the point. My main problem with Doctor Who is that it isn't really science fiction – not in the serious sense of the term. It's man against monsters for the imaginative enjoyment of children, rather than the exploration of deeper, grown-up themes as pioneered by the likes of Philip K Dick, Ray Bradbury, Arthur C Clarke or Ursula K Le Guin. It's all a bit panto, to be honest. I can see the appeal for children and young teenagers, and for their parents glad to have something to watch together, but for everyone else? Fortunately there is an alternative – and its name is Caprica.

Currently showing on Sky1, Caprica is a prequel to Battlestar Galactica – a sci-fi drama whose devotees believe it to be an even greater television show than The Wire. BSG, as it's known to the faithful, concerned a group of humans from a faraway colony who, having been attacked by a cybernetic race known as the Cylons, take to their spaceships in search of a fabled mother planet called Earth. It was a wonderfully rich, textured and holistic saga that can also be viewed as a wry commentary on the war on terror, as well as the inability of the human race to pull together even in extremis. A sort of sci-fi noir, Caprica is set 50-odd years before the events of Battlestar Galactica, and explores how the human colonists first developed the Cylons – as physical embodiments of virtual-reality avatars. And you don't need to be a BSG fan to follow Caprica.

Unlike Doctor Who, where the acting can be patchy, this series is strongly cast in depth. Eric Stoltz takes the lead role, as the wealthy scientist/industrialist and the creator of the Holoband, a device that allows wearers to enter virtual reality – a place where he can meet the avatar of his dead daughter, a rebel on an affluent planet (imagine ancient Greece crossed with Fifties America), who is blown up by her suicide-bomber boyfriend. Esai Morales plays the father of Battlestar Galactica's Admiral William Adama (here still a boy), whose wife and daughter have been killed in the same bombing.

Caprica delves into some pretty meaty themes, from religion and racism to terrorism and what it means to be human, while it directly addresses current developments with the internet and its virtual worlds. It's light years more ambitious in scope than Doctor Who, and it's still not too late to catch.

What does the future hold for Doctor Who? Is it unfair to compare a show aimed at a Saturday teatime family audience with one hoping to inherit Battlestar Galactica's sophisticated brand of sci-fi geek? The hopeful development for Tardis fans is that Doctor Who is now in the creative hands of Steven Moffat, who has succeeded Russell T Davies as its lead writer and executive producer. Moffat has penned some of the most bold and imaginative Doctor Who storylines (he wrote the excellent 2008 double episode "Silence in the Library"/ "Forest of the Dead") – indeed, Davies has said that although he always rewrote other episodes, he always left Moffat's well alone.

If anyone can take the series to a different level, then it is Moffat. We shall see. In the meantime, there is always this consolation. Whatever wrong turns Doctor Who takes in the future, it's unlikely ever to be as crummy as Torchwood.

'Doctor Who' returns to BBC1 on 3 April. 'Caprica' continues on Tuesdays at 9pm on Sky1