THERE'S ONLY one problem with "Betsy's Wedding." It's Alan Alda. But since he's the writer, the director and the father of the bride in the movie, that's a big problem.

In this Touchstone Pictures ceremony, Alda casts himself as a regular guy, a custom-home builder living in Long Island, who loves daughters Molly Ringwald and Ally Sheedy, wants to make love with wife Madeleine Kahn all the time and has a positive outlook that ignores all hardships. He's a Jimmy Stewart naif, as played by Hawkeye, the kind of wimpy, eager beaver you want to slap around and force to watch Home Team Sports.

Alda-the-creator (I use the term loosely) strains for the "artistic" heights of the later Woody Allen pictures, such as "Crimes and Misdemeanors," in which Alda appeared. But Alda's sitcom sensibility, which makes of everyone an open book of good, trivial intentions, undoes any such ambition. Alda wouldn't know deep if he drowned in it; he even falls short of Touchstone's lite-motif: generating riskless, middle-ground entertainment the way Nissan turns out little cars.

When pale 'n' puffy Ringwald and boyfriend Dylan Walsh suddenly announce wedding plans, it catches Alda unawares, because he has just overextended himself financially to build a house. He vows to give his daughter a big reception anyway, with a marquee, a band and hundreds of guests.

The announcement also sets up the prime-time-TV opportunity for a tired clash between cultures and generations: Ringwald's family is all-purpose ethnic (Alda's Italian, Kahn's Jewish); the groom's parents are rich, passionless WASPs. Ringwald and Walsh want a simple, intimate nonreligious ceremony in the living room. The WASPs and Ethnics want church, pomp and circumstance.

"My mother Rose," says Alda, introducing his Italian mama to Nancy, the groom's WASPish mother.

Nancy: "May we call you Rose?"

Alda's ma: "What else you gonna call me?"

How we laughed. How we cried.

That risky house venture, by the way, leads to further one-dimensional ethnicity when Alda asks sleazy brother-in-law Joe Pesci for a loan. Suddenly a mobster relative of Pesci's (hairy, mumbling Burt Young) is interested in the house, and dispatches wet-behind-the-ears nephew Anthony LaPaglia to oversee the project.

None of the performers (including Catherine O'Hara and, in the limpest of Allen-borrowings, Joey Bishop as the advice-giving ghost of Alda's dead father), can do much with the dross given them. Even Pesci, who injected engaging comic relief into "Raging Bull" and "Lethal Weapon II," is just an exasperating cliche.

Only LaPaglia comes close to pushing his character into something amusing, a sort of geeky Robert DeNiro. But in this movie, he's just another wedding guest.