To those of us who grew up in the wake of second-wave feminism, Mary Tyler Moore is a powerfully evocative figure. For this group, watching the HBO documentary “Being Mary Tyler Moore” may prove an emotional experience, conjuring nostalgia of two distinct types: the gentle sort involved in remembering a beloved star of the past, and a more painful nostalgia provoked by recalling a time when womanhood seemed to beckon with new, liberating possibilities, and feminism seemed on a steady path forward.

In her most famous role, as Mary Richards on her self-titled 1970s television show, Ms. Moore offered a dazzling new model of female adulthood: a confident, beautiful unmarried woman over 30, who supports herself, wears fabulous clothes, finds fulfillment through work and friendship, and enjoys an active love life with no apparent anxiety about finding a husband.

As Rosie O’Donnell comments in the film, this image of a woman making her own way in life was “seared” into her brain. Katie Couric concurs, noting that Ms. Moore’s example “opened my eyes to ‘wow, I want to do that too.’”

“Who can turn the world on with her smile?” the show’s memorable theme song asked — a question then answered with the opening montage of Marys — laughing with friends, strolling city streets and, of course, exuberantly throwing her tam into the air. The point was clear: Mary smiled at the world and it smiled back, welcoming this character into a big life extending far beyond the domestic realm.

“The Mary Tyler Moore Show” marked a transition in television roles for women, turning the page on all the dutiful wives and mothers, marriage-minded girls and those characters perpetually struggling to transcend their narrow lives: Lucy Ricardo (yearning for show business), Jeannie on “I Dream of Jeannie” (magical, yet living in a bottle and pining for a man) and Samantha Stevens on “Bewitched” (again, magical, yet confined to a suburban colonial).

Ms. Moore’s career played out a version of that transition. She entered television right out of high school, as Happy Hotpoint, a dancing, leotard-clad pixie singing the praises of Hotpoint kitchen appliances on “The Adventures of Ozzie and Harriet” — a literal embodiment of feminine domestic labor on the most traditional of family sitcoms.

Then, as Laura Petrie on the “The Dick Van Dyke Show” in the 1960s, Ms. Moore loosened some of the typical sitcom wife’s restraints: She danced and sang; she was funny; she had opinions; and at Ms. Moore’s insistence, she swapped out the usual June Cleaver-esque uniform of dresses, pearls and heels for sweaters, flats and trousers that showed off her trim figure.

But as Mary Richards, Ms. Moore became an icon. She made “a feminist statement that got into my bones,” Julia Louis-Dreyfus observes in the film. The show’s commitment to women was palpable, foregrounding women’s friendships (Rhoda! Phyllis!), treating timely issues like contraception, pay equity and feminism, and — according to the documentary — employing more female writers than any sitcom had before.

The documentary frames Ms. Moore’s life in the context of the women’s movement, interspersing footage of feminist rallies, news stories about Roe v. Wade and clips of Gloria Steinem and Betty Friedan. But while Ms. Moore’s TV self seemed fully in step with feminism, her personal life was more complicated. “She didn’t think feminism was so hotsy-totsy,” says Ms. Moore’s close friend, the actress Beverly Sanders. “She identified with it, up to a point.”

Unlike the boldly single Mary Richards, Ms. Moore had been married virtually her entire adult life. She wed first at 18 and had her only child, a son named Richard; divorced; and soon thereafter married the producer Grant Tinker, who masterminded her career and with whom she founded MTM Enterprises, her wildly successful production company. Not particularly independent at that time, Ms. Moore admitted that she relied heavily upon Mr. Tinker’s judgment: “I was very much a person who liked being directed and led.”

Significant challenges beset her years with Mr. Tinker. She suffered a miscarriage and then, at 34, was diagnosed with Type 1 diabetes (whose complications plagued her for the rest of her life). She also battled alcoholism.

In 1978, her younger sister, Elizabeth, died by suicide. And most painful perhaps was her distant relationship to her son, with whom she struggled to connect. Friends note often in the film that, offscreen, Ms. Moore could seem aloof and detached, unlike her onscreen upbeat self.

“The Mary Tyler Moore Show” ended in 1976, and Ms. Moore embarked on a new, Mary Richards-style chapter in her personal life, divorcing Mr. Tinker and moving alone to New York City. Professionally, though, she left Mary Richards far behind and turned her attention to theater and film, proving especially gifted at serious drama.

In 1980, Ms. Moore won a special Tony for her portrayal of a quadriplegic hospital patient in “Whose Life Is It Anyway?” And she was nominated for an Oscar for her subtle performance in Robert Redford’s directorial debut in 1980, “Ordinary People,” as Beth, an emotionally closed mother grieving one son’s death and coping with the attempted suicide of the other.

Ms. Moore saw Beth as “reminiscent of my own life,” but could never have guessed how much like her life the film would turn out to be. Three weeks after its premiere, Ms. Moore’s son, then 24, was found dead of a self-inflicted gunshot wound, which was determined to be an accident.

In subsequent years, Ms. Moore strove to break through her pain and emotional walls. In her late 40s, she married Robert Levine, a physician 18 years her junior who didn’t know who Ms. Moore was when they met. The marriage lasted 34 years, the rest of her life.

“She married a regular person,” notes Manny Azenberg (the producer of “Whose Life Is It Anyway?”), and that regular-ness seemed exactly what Ms. Moore needed. Footage of the couple relaxing at the ranch they owned provide the most moving and genuine images of the entire documentary, showing an unplugged, makeup-free Ms. Moore running around in casual clothes, teasing her husband, tending lovingly to the horses and dogs she kept.

During that time Ms. Moore found the strength to tackle her drinking. She checked herself into the Betty Ford Center, an experience she described as “chiseling down to the real me” — the use of “chisel” suggesting just how unyielding the surface felt to her. While in rehab, she said, she learned “it’s not the end of the world if I’m not perfect. I never really confided in people, and I never shared any of the ugly sides.”

The confession was telling. Had the need for perfection been suffocating Ms. Moore? While surely her own life and past created much of her personality, what role did her career play in this? What damage is done to those, especially women, we turn into idols — even idols ironically of feminist freedoms?

In one moving clip in the documentary, Ms. Moore makes a surprise appearance on “The Oprah Winfrey Show” (Ms. Winfrey was apparently unaware she was coming). Visibly overcome with emotion, eyes brimming, slightly trembling, Ms. Winfrey rushes to embrace Moore. “You have no idea what you’ve meant to me!” she says.

Ms. Moore is warm and gracious. She likely had a good idea of what she meant to all the former little girls and teenagers who’d projected so much aspiration and ambition onto her, or rather onto a fictional character she played.

Being Mary Tyler Moore was never the same as being Mary Richards, but for millions of women the distinction is blurry. Maybe we need it to be. “Mary” was aspirational for many of us at a time that really mattered, at a crossroads in American women’s history. Yes, she was unrealistic, idealized and still conforming to certain narrow parameters of beauty, class and race. But she was what popular culture offered us — and that mattered, a lot.

There are no on-camera interviews with living people in “Being Mary Tyler Moore.” In part, this is because most of those featured, including most of her TV castmates, have died (Ms. Moore herself died in 2017 at 80).

But even those still alive appear only as voice-overs, narrating footage from years ago. This grants the film a nostalgic preserved-in-amber effect, situating Ms. Moore’s life firmly in the past. But it sets the world she represented firmly in the past too, reminding us that the historical moment when feminism’s progress seemed assured has vanished. That inspires quite another type of nostalgia — and it hurts.