Mary Tyler Moore, Mary Tyler Moore -- Say, didn't we used to LOVE her? Yes and no. We loved her show. We loved the group around her. We loved the way she said, "Oh, Mr. Grant." We loved Mr. Grant.

But comes now "The Mary Tyler Moore Hour." her second attempt within a season to prosper in a variety format on CBS, and something about sweetums has turned a little sour. She has become the formerly wonderful Mary Tyler Moore, and the show, premiering at 10 Sunday night on Channel 9, seems disingenuous and disenchanting, with a script so silly it's reactionary. It's "My Little Mary."

CBS calls it "a show-within-a-show." Its more of a show without a show.

Veteran producer Perry Lafferty, called in after Mary's First Flop, has labelled the format "sit-var," since it's a plot comedy which allows for musical numbers, chiefly because Moore is playing Mary McKinnon, an innocuous TV personality not unlike herself. The storyline of the first show is wheezily old-hat; McKinnon goes out on a limb to snare Lucille Ball as a guest star for her "snow."

Jack Benny's writers used to send him out on such perfunctory errands occasionally, but everywhere that Benny went, an arsenal of exploitable and cherished comic traits went with him. With Moore, expectations are considerably more vague and less rich; as a comic character, about all she has is her die-hard but tiring innocence.

So the writers have her getting drunk on Irish Coffee at a Beverly Hills boutique where Ball is trying on clothes. Soon, bombed, they stumble off to the Mike Douglas Show, where they share the stage wih a Japanese cook who makes them eat baby eels and octopus.

It would take a great clown to put over a pretext this slim and frivolous. Of course, there is a great clown on the premises, and even though time may have withered, custom has not staled Lucille Ball. Her final grimace and shudder as the eel slids down her throat are reminders of the most exquisite physical comedienne ever to work in television.

By comparison, Moore's drunk act is feeble and hald-hearted; she seems to have modeled it on Sandy Dennis's performance in "Who's Afraid of Virginia Woolf?", which was not exactly an invitation to merriment.

The hour opens and closes with musical numbers, both handsome and splashy. In the first, Moore is chromakeyed into a scene from "Way Out West," in which Laurel and Hardy paused in mid-movie to sing and dance in front of a saloon. Unfortunately, the technical feat of teleporting Moore into this scene proves more arresting than her performance, which has the aura of an impertinent intervention into a work of art.

The writers, in their folly, have sought to give Moore another "family" of adorable eccentrics. Most of them are grating, repugnant creations -- especially Michael Lombard as McKinnon's loud-mouth producer, involved in a pointless and extraneous subplat that will interest no one. However, Michael Keaton, by far the standout in the repertory company assembled for Mary's Fall Fiasco, has been held ove, and he continues to be a source of inventive support.

Moore's new show opens with an instrumental version of her old "Mary Tyler Moore Show" theme -- the producers taking no chances in their quest to remind us how much we loved Mary before.

Moore herself walks around with a big "remember me?" grin on her face. But if there had been no previous program, and if there were not some residual good will toward Moore hanging around, this new variety hour would never have seen the light of television. It amounts to a desperate step backward. 'Just Friends'

Stockard Channing, the lone enlightened spirit of the loathsome movie "Grease," reportedly did not want her new CBS comedy series, premiering Sunday night at 9:30 on Channel 9, called "The Stockard Channing Show." So she settled for the presumably less presumptuous "Stockard Channing in Just Friends."

Whether the negotiations that produced that compromise took place at Camp David, we do not know.

The program, written by Nick Arnold and Eric Cohen, is, like all premieres, crowded with the introduction of characters who must establish their whackiness in just a few lines of dialogue, but also buoyant and promising thanks to the cheeringly velnerable Channing. She is a prize package.

"Just Friends" is not heavy-laden with ideas, or even much of a premise -- Susan Hughes (Channing) leaves her dullard husband in Boston and seeks new independent life in Los Angeles among local vegetation. But the writing is a notch more clever than the norm, and the supporting cast is brisk and compatible.

As Channing's snobbish and aloof sister Victoria, Mimi Kennedy is particularly funny and brazenly Bryn Mawr. There is a perfection beyond perfection to her line readings of Oh Sue-zunn, all right, live on your own" and "Oh Sue-zunn, I'm sorry your marriage failed."

Channing's facial reactions to the addled or boorish people she must contend with are in the best TV comedy tradition, and she also gets a semi-weepy telephone scene to help make her character more than just another Rhoda or Angie. "Just Friends" is just ducky.