You can’t go wrong with picture-postcard views of the capital of France, and Woody Allen luxuriates in them in his new movie—the first few minutes, in fact, consist entirely of a montage of shots of the city’s scenic locales stretching from early morning to night. But narratively “Midnight in Paris” is a frail conceit that Allen fills out with humor that’s surprisingly obvious and broad.

The piece is about nostalgia, though the stance it takes about love of the past is muddy at best. Owen Wilson is the inevitable Woody surrogate, a successful but flustered Hollywood screenwriter named Gil who’s trying to write a real novel. He travels to Paris with his fiancee Inez (Rachel McAdams) and her parents, obnoxious businessman John (Kurt Fuller) and his snarky, money-mad wife Helen (Mimi Kennedy). As if his prospective in-laws weren’t sufficiently annoying, Gil has to the presence of one of Inez’s old friends, insufferably pedantic Paul (Michael Sheen), who shows up with his girlfriend Carol (Nina Arianda) and insists on spending time with Inez and Gil, or preferably just Inez.

Gil decides to go off walking alone, and precisely at midnight he’s invited into an old cab that transports him to his favorite Parisian epoch—the 1920s—and finds himself cavorting with the likes of F. Scott and Zelda Fitzgerald (Tom Hiddleston and Alison Pill), Ernest Hemingway (Corey Stoll), Cole Porter (Yves Heck), Pablo Picasso (Marial Di Fonzo Bo), Gertrude Stein (Kathy Bates), Salvador Dali (Adrien Brody) and Luis Bunuel (Adrien de Van). But he’s especially taken with the beautiful Adriana (Marion Cotillard), Picasso’s current lover. The time-travel delight is so great—and so helpful to his writing—that Gil keeps returning to it night after night. Naturally this causes a strain on his relationship with Inez and her parents.

There’s a further wrinkle to the issue of whether nostalgia like Gil’s is really all that good when he and Adriana find themselves whisked back to her favorite era—La Belle Epoque, where they meet figures like Toulouse-Lautrec and Degas. And you can be sure that Gil will ultimately break off with Inez, who’s portrayed by McAdams as a shrill, unsympathetic type (and whose parents are depicted as smug right-wing nut jobs), though whom he finally winds up with may come as a surprise to some (though, I expect, not many).

Ultimately “Midnight in Paris” is about the danger of obsessing about the past so much that you forget to live in the present. Fair enough, even if the message is muddled by Gil’s unhappy here-and-now. But it’s also weakened by Allen’s portrayal of Gil’s dream of the 1920s. One could be satisfied with either a really sophisticated, witty depiction with vibrant versions of the historical characters, or a complete send-up. But other than Adrien Brody’s hilarious take-off on Dali, what we get are half-baked caricatures who mouth not very scintillating lines of dialogue. It’s as though they’d all been conjured up by the sort of hack scriptwriter Gil seems to be in the first place. (In fact, if that suggestion had been made, the whole thing might have worked.) As it is, though, it comes off as little more than an extended edition of “Drop That Name.” (Remember “Bells Are Ringing”?)

So what are we left with? A mildly diverting fantasy, executed without much style. An amiable performance by Wilson, who doesn’t make the mistake Kenneth Branagh did in “Celebrity” of trying to mimic Allen. An occasional smart bit of dialogue. Some lovely settings. But there’s too often a feeling that Allen is pandering to the audience, patting them on the head simply for recognizing these famous folk or their turns of phrase and shooting off entirely too easy put-downs of Tea Party types and ugly Americans abroad.

In closing, you might want to check out an old TV take on nostalgia that’s crisper and more affecting than Allen’s slight tale. It’s a “Twilight Zone” episode by Rod Serling called “A Stop at Willoughby,” in which James Daly plays a harried ad agency executive who dreams that his commuter train keeps stopping at the quiet, restful nineteenth-century town of the title. Eventually he decides to get off there, and while giving away Serling’s twist would spoil things (watch it for yourself!), suffice it to say that his denouement is a lot more pointed than the one you’ll find here.