In an alternate, more dispiriting universe than this one, Naomi Watts is up for an Academy Award this year for her portrayal of Princess Diana in “Diana.” (I think it’s that universe where Spock has a goatee.) It should have been this year’s “The Iron Lady” or “My Week With Marilyn,” a not-very-good hunk of Oscarbait built around an act of historical impersonation.

Instead, “Diana” never played in Madison theaters (despite trailers showing at Sundance for months), and slunk onto DVD last week. What went wrong?

First and foremost, the movie is an undeniable dud, turning the last couple of years of Diana’s life into a gauzy and tawdry soap opera. Beginning with an icky scene that shows us Diana’s last few moments before she got into that car in Paris, the rest of the film backs up and takes place between 1995 and 1997, post-Charles. Charles doesn’t appear and her sons are barely mentioned, I’m guessing for legal reasons, which severely limits the scope of the film.

The life of a real-life princess seems — kind of boring, actually. She wears nice suits and jets back and forth around the world, giving speeches here, interviews there. She bemoans the paparazzi hounding her. And she starts a relationship with a handsome but bland surgeon, Hasmat Khan (Naveen Andrews of “Lost”). The film wants to present Hasmat as her one great love, but Andrews and Watts generate little more than polite chemistry onscreen, despite overheated chick-lit dialogue.

When Hasmat finally can’t commit to her because of her fame, the film suggests Diana starting dating playboy Dodi Fayed largely to make him jealous, even arranging those compromising paparazzi shots of her on his luxury yacht. This is all largely speculation, of course, a Page 3 InTouch Weekly article turned into a movie.

The second knock against “Diana” is that Watts’ performance just isn’t that good, although some of that is out of her control. She doesn’t really look like Diana, despite the presence of a small prosthetic nose. And Watts isn’t asked to really sound like Diana, except when the film exactingly recreates one of her famous public appearances, such as that “Queen of people’s hearts” interview. Those re-enactments are very weird, by the way, and suggest that the filmmakers were going for sort of a greatest-hits collection rather than an insightful biopic.

The real problem is that “Diana” wants to lionize Diana on one hand and dish on her on the other, and that leads to a film without any consistent point of view about her at all. Diana comes off as a caring and savvy woman in one scene, using her fame to draw attention to landmines in Angola, and in another scene seems like a scheming adolescent.

Contradictions between a public and private self can add depth to a character, but “Diana” is so torn between tabloid chatter and middlebrow hagiography that it resists Watts’ attempts to humanize her. Somehow, one of the most famous faces in the world, one that the New Yorker devoted an entire issue to after her passing, seems paralyzingly dull.