“Tootsie” had everything going for it: great title, terrific reviews, star-making turn by Santino Fontana, snappy score by David Yazbek and a hilarious book by Robert Horn.

And yet one of the best musical comedies to come around in a long time is a flop. “Tootsie” opened in April and will close Jan. 5 without returning a fraction of its $10 million production cost.

“I’m sad,” says Horn, who won a Tony for his book. “I honestly thought we would become this staple, a big musical comedy that people would go to. But she’s a fickle mistress, this theater world.”

She is indeed, but let’s try to figure out why her fickleness cast “Tootsie” into the dark.

For starters, “Tootsie” is a great title for people over 50, many of whom saw the movie when it came out in 1982, and loved it. But a new generation is going to Broadway shows, and the kids who love “Wicked” and “Mean Girls” have never heard of “Tootsie.”

That generation is going to “Beetlejuice,” which got indifferent reviews, but is now catching on. It did more than $1 million last week at the Winter Garden. The Shuberts are throwing it out next year to make way for Hugh Jackman in “The Music Man,” but they might want to make a deal to transfer it to another theater. “Beetlejuice,” slimmed down for a smaller theater, could be a nice little earner.

Also, as one Tony voter, who voted for “Tootsie” as Best Musical, says, “It’s very satisfying as a comedy, but not very satisfying as a musical.” What he means is that Yazbek’s score doesn’t quite reach the heights of Richard Rodgers or Andrew Lloyd Webber. Yazbek wrote funny, sophisticated songs, but what’s missing is a melody you can latch on to — a melody such as “Some Enchanted Evening” or “Memory.”

I know Yazbek can do it. “Omar Sharif” and “Answer Me,” two songs he wrote for “The Band’s Visit” are gorgeous. The songs for “Tootsie” are good, but they don’t soar the way those do.

Another factor: “Tootsie” is about showbiz, and shows about showbiz have a limited life. “The Producers” was the blockbuster hit of 2001, but ran a mere six years. “The Phantom of the Opera” and “Wicked” are still running.

“Shows about showbiz are hard to sell,” says Horn. “But I can’t speak for the masses. I love going to the theater to see a show about the theater.”

Finally, the time for “Tootsie” may have come and gone. “It’s about a self-centered guy who dresses up as a woman to take a job from a woman,” says a source on the show. “Three years ago, it would have been hilarious. Today, I’m not so sure.”

That said, “Tootsie” is a fun show, and you should see it before it closes.

“I have nothing but love for the show,” says Horn, who’s work is in demand, thanks to that Tony. “After so many years of, ‘Who is this guy?,’ I’m fielding offers. And I’m in the lovely position of being able to say no. But you’re going to hear about some things I’m involved in very soon.”

“Len Berman and Michael Riedel in the Morning” airs weekdays on WOR Radio 710.