A Kinder, Gentler Robin in ‘Doubtfire’ : The comic continues to forsake his trademark anarchy for more warm and cuddly roles.

We’re losing Robin Williams.

Never mind that his latest film, “Mrs. Doubtfire” (citywide), has the markings of a major commercial success, an achievement due exclusively to Williams’ agreeing to take on a role born in high-concept heaven: A divorced dad disguises himself as a grandmotherly British housekeeper to spend more time with the children he loves.

And, of course, when Williams wants to be funny, no one can hope to keep up. Whether mimicking Gandhi or Porky Pig, doing a wicked two-step with a vacuum cleaner or ad-libbing a dinosaur-oriented rap lyric, Williams is one of the rare performers who defeats even superlatives.

So what’s the problem? It’s that “Mrs. Doubtfire” underlines a trend in Williams’ work that can’t be ignored. Probably the preeminent comic talent of his generation, he is less and less involved in being funny on screen. Losing interest in his trademark anarchic verbal horseplay, he is leaning increasing toward warm and cuddly roles, as if Lenny Bruce had slowly turned into Mr. Rogers. Gradually but undeniably, Williams is going soft and mushy, and it is not a pleasing sight.

This trend is not a new one, of course, but when “Dead Poets Society,” “Awakenings” and “Hook” were followed by the cloying “Toys” and now this, the momentum is inescapable. Even when, as with “Mrs. Doubtfire,” Williams’ performances come with humor attached, his work feels hybrid, as if the sentiment is leaking through and denaturing the strength of the comedy.

A “Tootsie” for the single-parent set, “Mrs. Doubtfire” (rated PG-13 for “some sexual references”) is unobjectionable enough, a safe and sane entertainment where all the characters are nice and all the situations unadventurous. Anyone looking for the kind of comic brio that Dustin Hoffman and company brought to “Tootsie” will not find it here.

Williams’ character, voiceover actor Daniel Hillard, is amusingly introduced providing the vocals as cartoon character Pudgie the Parrot sings Rossini’s celebrated Figaro aria. Daniel is clearly good at his job, but soon he is out of it: Determined to put a socially conscious anti-smoking message in Pudgie’s non-moving lips, he becomes one more unemployed but caring San Francisco guy.

What Daniel cares most about are his three kids, and who wouldn’t, given that each is sweeter than the next. The only spoilsport in this happy family turns out to be wife Miranda (Sally Field), a high-powered, dressed-for-success interior decorator who for 14 years has been making the rules that elfin Daniel can’t resist breaking.

No sooner do we meet this group than Miranda, after a particularly egregious breach of discipline, tells Daniel enough is enough, she wants a divorce. The kids are shocked, but in truth it’s not any less plausible than those supposed 14 years of Williams/Field togetherness or the fact that a killingly handsome millionaire (Pierce Brosnan) suddenly appears as Miranda’s suitor. Out of a job, without a place to live, Daniel can only watch in horror as his wife is granted custody of the children.

But when busy, busy Miranda announces she has to hire a housekeeper, Daniel sees his chance. Helped by brother Frank (Harvey Fierstein), who just happens to be a wizard of a makeup artist, he disguises himself as Mrs. Doubtfire, a kindly but no-nonsense elderly party who soon makes him/herself indispensable in the Hillard household.

The source for “Doubtfire’s” Randi Mayem Singer and Leslie Dixon script turns out to be a children’s book by Anne Fine, and the result is a film with too many traces of that genre’s soft edges. Not helping is youthful “Home Alone” director Chris Columbus, who already has the kind of complacently commercial sensibility it usually takes years to develop.

And then there is Williams. Even though, unlike Hoffman in “Tootsie,” his disguise is so foolproof it takes part of the fun out of the role, even though his too numerous speeches about being a good dad are more earnest than effective, when he allows himself to be funny there is no one else you want to see.

So, once again, why care? Clearly no one is holding Williams’ hands to the fire to play these parts, he must enjoy taking on saccharine characters, and complaining about the situation leaves one open to the kind of scorn Woody Allen showed his critics in “Stardust Memories” when he had space aliens say they were fans of his earlier, funnier movies.

But Williams is not enlarging his scope, as Allen did, he is constricting himself by appearing in increasingly bland and sappy motion pictures. And as film succeeds film, the chances of a reprise of the kind of daring, coldly brilliant cameo he did in Kenneth Branagh’s “Dead Again” seem increasingly unlikely.

Maybe this was inevitable, maybe, like Zero Mostel, Williams’ true performing personality is too large even for the big screen. Still, if for instance Spanish painter Francisco Goya had abandoned his brilliant series of etchings and devoted his life to being a competent maker of decorative tile, those who cared about the field he left behind would have felt it a shame, and so it is with Mr. Williams.

‘Mrs. Doubtfire’

Robin Williams: Daniel Hillard/Mrs. Doubtfire

Sally Field: Miranda Hillard

Pierce Brosnan: Stu

Harvey Fierstein: Frank

Robert Proskey: Mr. Lundy

A Blue Wolf production, released by 20th Century Fox. Director Chris Columbus. Producers Marsha Garces Williams, Robin Williams, Mark Radcliffe. Executive producer Matthew Rushton. Screenplay Randi Mayem Singer and Leslie Dixon, based on the novel “Alias Madame Doubtfire” by Anne Fine. Cinematographer Donald McAlpine. Editor Raja Gosnell. Costumes Marit Allen. Music Howard Shore. Production design Angelo Graham. Art director W. Steven Graham. Set decorator Garrett Lewis. Running time: 2 hours, 8 minutes.

MPAA-rated PG-13 (some sexual references).