At this point, I would love to tell you that “Diana” has been mistreated or even misunderstood, that there”s more to its apparent absurdities than meets the eye – if only because all the best quips about it have already been cracked, making the film pretty threadbare carrion as it limps into U.S. theaters this week. Alas, I can only confirm that “Diana” is every bit as risible as you”ve already heard, and not in the deludedly overambitious way that makes for fascinating folly – Madonna”s similarly inept “W.E.” handily trumps this for both ostentatious formal bloat and high-camp hilarity.

No, what”s particularly dismaying about Hirschbiegel”s film is that it fails so dully, and at such an achievably middlebrow target: lit and staged like daytime drama, “Diana” sets out to offer little more than a potted, soap-opera snapshot of the late Diana Spencer”s post-divorce romantic reawakening. In focusing principally on her brief affair with Pakistani heart surgeon Hasnat Khan, the film is arguably taking on one of the less intriguing stretches of the princess”s botched fairytale life, though it is at least one of the less-covered ones; die-hard royalists seeking salacious family details would be best advised to look elsewhere. (A brief glimpse of the young William and Harry aside, the Windsors are not in evidence.)

Perhaps writer Stephen Jeffreys elected to tell this particular story as a route to examining the woman behind the princess, removed from the angst and institutional formality of palace politics – much of the film plays as a kind of stiffly whimsical “Roman Holiday” riff, with Diana out to prove her realness in a variety of embarrassingly contrived setups: a disastrous attempt at cooking a romantic dinner (see, she”s just like Bridget Jones!), or donning a mangy dark wig for a paparazzi-free night on the town in London”s gay quarter. She”s a wild one, that Di. Still, the film”s separation of her supposedly private persona from her public one is as unconvincing as her Sydney Bristow-style disguise: how can the film profess to show us the complete woman while strenuously skirting her family life or past psychological torment?

In focusing specifically on Diana the lover – who, in her pushy seduction technique, pays nominal respect to her mythological namesake, the goddess of hunting – Hirschbiegel might have been better adopting the dispassionately domestic perspective of his remarkable Hitler biopic “Downfall,” which achieved genuinely fresh insight into a larger-than-life historical figure through patient scrutiny and mundane personal detail. Alternatively, playing the “last great love” angle for florid Sirkian melodrama might have rendered the woman more human through exaggeratedly expressive emotion.

Jeffreys” glib, magazine-profile script blandly takes the middle path, relentlessly flattering its subject without demonstrating any clear interest in examining her. Actual characterization, it seems, would be tantamount to disrespect. What we get is a lighter, flightier Diana than the image we”re accustomed to, but that doesn”t make her any more human – particularly when the core love story is played, beat for beat, as swoony romantic fantasy from the Richard Curtis playbook.

After a morbid intro in a claustrophobic hotel corridor that gauchely foreshadows the circumstances of her tunnel-set death hours later, Hirschbiegel jumps back two years to her sickly meet-cute with Khan (Naveen Andrews, performing as if under duress) in a hospital, as he walks her through the not-at-all-metaphorical process of mending human tickers. “Hearts can”t actually be broken?” she simpers incredulously. Suffice to say Jeffreys” barely Harlequin-level dialogue does little to counter the widespread perception that Diana was, for all her grace and glamor and goodness of spirit, a bit dim.

This sets the tone for the rest of their dippy courtship, with extra reserves of synthetic earnestness brought out for a stint of anti-landmine activism in Angola, dramatized with all the specificity and soul of a telethon plea. Jeffreys can”t even claim credit for the film”s single most ludicrous (and therefore best) line, a bit of pillow talk filched by Khan from the Persian poet Rumi: “If you can”t smell the fragrance, don”t come into the garden of love.” By that point, “Diana” could benefit from more of this unabashed kitsch.

Cornered by such unilluminating writing and uninvested direction, Naomi Watts has little option but to play the princess as a kind of mystically smiling cipher, a doll with supremely well-functioning eyelashes. As an impersonation, it”s adequate: she looks the part, which is to say she”s pretty enough, dressed in devotedly duplicated costumes and has the requisite swadge of yellow hair, though there”s little attention paid to vocal or gestural detail.

But there”s no heart here for her man to mend: if anything, the performance”s occasional surface accuracies only highlight how distant and disconnected from us the rest of this plastic princess feels. A number of my colleagues have inevitably revelled in dubiously tasteful car-crash metaphors to describe “Diana.” They”re forgivable, if only because the film itself is scarcely less crass, but they”re also off the mark: this drearily inert hagiography could only crash if it were in motion to begin with.