Have you noticed that you’re not watching HBO on Sunday nights anymore? Let’s hope HBO has. That once was a magical time slot for the pay-cable channel; such television classics as “The Sopranos,” “Sex and the City,” and “Six Feet Under” found an audience among discerning watchers who’d grown tired of the broadcast networks’ meager Sunday night fare. But “Sex and the City” is gone, “The Sopranos” won’t be back until 2006, and “Six Feet Under” has just announced that its next season will be its last. Adding to the problem – and underscoring HBO’s sudden and dramatic lack of product – is the runaway success of ABC’s “Desperate Housewives,” a mediocre show that HBO could have done smarter and better.

But HBO passed on “Desperate Housewives,” probably because it didn’t fit into its increasingly star-driven mentality. (“Not gritty enough” is how the show’s creator, Marc Cherry, recounted HBO’s official response.) In recent months, HBO has made new series deals with Lisa Kudrow, Courteney Cox, George Clooney, Brad Garrett, and Diane Keaton. They’re all smart actors, but they’re not writers. Darren Star – the creator of “Sex and the City”- may not deliver poetry, but at least he’s a writer who does his thinking in front of a computer screen, not in a movie-star trailer or on the phone with his agent. Ironically, HBO may soon end up in the same fix the networks find themselves in every so often, when they program their schedules around big stars instead of smart concepts. It’s the road to ruin.

Where did HBO go wrong? It’s hard to pinpoint exactly, but I’d say the low point had to be the day “Sopranos” creator David Chase announced he wasn’t even going to start writing the sixth season of his classic series until next year, delivering episodes sometime in 2006. That’s when the HBO executives overplayed their hand; after years of collecting piles of Emmys and reams of positive reviews, they mistakenly convinced themselves they could keep the “Sopranos” audience in place for the two-year gap between seasons with whatever concepts they approved. The lukewarm reviews for “Deadwood” and “Carnivale” didn’t deter them from their outsized belief in their own genius. And it got to the point where just about anything HBO put on the air – even this fall’s tedious and repetitive reality series “Family Bonds” – could interest some critic in raving about it. I’m one who succumbed, briefly, to the charms of “Carnivale,” though in its yearlong absence I haven’t found myself yearning for a second season.

The arrogance of HBO is understandable. Beginning with “The Larry Sanders Show” and continuing with “Oz” through “Curb Your Enthusiasm,” it has been home to some of the freshest concepts on television. Its support of writers like Mr. Chase, Larry David, Tom Fontana, and Alan Ball has earned HBO enough credit in the television community to last for years. By the late 1990s, it had evolved into a must-have channel for anyone who appreciated good television, and not only with series; its documentaries, movies, and special events (most notably last season’s “Angels in America”) were essential viewing. The financial support of HBO to artists who might otherwise go homeless on television was not only commendable, it was an essential part of the medium’s growth. The leadership of Jeff Bewkes and Chris Albrecht led to an explosion of creativity unparalleled elsewhere.

But lately, HBO has fallen too in love with itself. It can’t help but be flattered by all the talent vying for its attention and support; I don’t blame them for wanting to be in business with the gaggle of celebrities who now have HBO shows in development. But is that what it really wants to do – be the home to the pet projects of only the people in Hollywood with the clout to land a meeting with the HBO development team? If there’s one thing the success of “Desperate Housewives” proves, it’s that the strength of an idea can easily trump the credentials of the writer-producer. A year ago, most network television executives could barely recall Marc Cherry’s credits; today, they’re all in line to be his best friend.

Maybe HBO needs to look beyond the credentials and the glitter, and conduct a hard-target search for ideas that work – regardless of who’s attached, involved, or available for lunch. Before David Chase created “The Sopranos,” his biggest credit was a stint on “The Rockford Files.” When Darren Star came up with “Sex and the City,” he’d just come off a disastrous year producing the CBS series,” Central Park West. “Okay, so Alan Ball had just gotten an Academy Award for his “American Beauty” screenplay, but his television experience was limited to sitcoms like “Cybill” and “grace Under Fire.” What made these men so appealing to HBO was the power of their ideas, and the strength of their execution. While it’s true that “Deadwood” and “Carnivale” also represent leaps of faith in support of smart writers, both shows seem more like concepts developed by writers to fit into HBO’s arbitrary sense of itself. The channel has become the official home for gritty series about conflicted characters in unpredictable settings – battles between good and evil set against epic backdrops. It’s an interesting but excessively narrow pigeonhole.

I’ve learned never to underestimate HBO’s ability to astound me, and I won’t be surprised if a great new show arrives within the next year or two. But I hope the men and women who run HBO aren’t so busy cavorting with stars to notice that the channel doesn’t own Sunday nights at 9 anymore; they need to come up soon with something good enough to wrestle it back from ABC. If they wait until Mr. Chase gets around to delivering the next season of “The Sopranos” in 2006, it may be too late.