Mark Ruffalo (left) and Taylor Kitsch in “The Normal Heart.” (Jojo Whilden/HBO)

What luck to have lived long enough to blithely watch an HBO movie adaptation of Larry Kramer’s 1985 play, “The Normal Heart,” from the vantage point of 2014, where the HIV and AIDS epidemic can be included on a list of crises abated. (Or at least be seen as a crisis kept at a remove for those who have access to expensive wonder drugs.)

“The Normal Heart,” no matter how powerful or moving it may still be, exists in a retrospective context. It’s a strange encounter; any perspective feels like a dodged bullet to Americans who came of age under a cloud of sexually transmitted plague.

This new version of “The Normal Heart,” directed by Ryan Murphy (“Glee,” “American Horror Story”) from a successfully revamped screenplay by the 78-year-old Kramer, captures the urgency and righteous outrage that the author first intended 30 years ago. Everything about “The Normal Heart” (premiering Sunday night on HBO) is handled with the tender, loving care owed to the elders.

Kramer brings his play into a fresh and cinematic relevance, exchanging some of his and his characters’ stagey shrillness (once a necessary weapon in a war of words) for a hint of what AIDS meant to the larger history of homosexuality and vice versa. The immediacy of the original turns into a longer reach for permanence; Kramer’s edits help the film version speak directly to the present and the past.

But it’s not clear that everyone involved got that message and instead just heard that the movie would be important. This makes it susceptible to that true leftover artifact from the AIDS era — the red ribbon-wearing grimace of Hollywood’s dutiful concern, certain to be rewarded when the prime time Emmy nominations come around. Perhaps it’s impossible to make a “Normal Heart” movie that people would watch all the way to the end because they want to, not because they feel like they have to.

A heavy sense of obligation runs through Murphy’s direction — through every word, every inflection, every choice, every time a new-wave dance hit becomes an ironic dirge. It doesn’t leave much room for ambiguity or surprise. Even visually, Murphy so assiduously avoids delivering a period piece that his film forgets to impart enough of what it felt like to be in New York in the ’80s. That’s a completely understandable artistic choice — the words and the people are more important than the nominal wardrobe and prop touches; but the blandness and seriousness deprive the movie of texture. Viewers often get the sense that we’re being taken into a stone monument that should have already been built years ago.

As such, everything that’s excellent about “The Normal Heart” — including compelling performances from its stars, Mark Ruffalo and Julia Roberts, with an especially strong turn from “White Collar’s” Matt Bomer — is also merely just fine; very good but not great; a tear-jerker but not a bawler; and probably beyond reproach.

Ruffalo plays a writer named Ned Weeks, whose conflicted ideas about hedonism and sexual liberty make him both a participant in the bathhouse culture and a bummer on the dance floor. It’s the summer of 1981, and the Fire Island party scene barely takes notice of a short New York Times article describing a mysterious and fatal “gay cancer” spreading among men in Manhattan. Ned certainly notices, and soon he’s in the offices of Dr. Emma Brookner (Roberts), who busily documents cases, cares for the dying and shares Ned’s tendency for the raised voice.

“The Normal Heart,” as theatergoers know, is a streamlined narrative of the gay New York experience at the earliest onset of the disease’s spread. Ned is a stand-in for Kramer himself, who is never wrong and who, with several other men, formed what became an organization called the Gay Men’s Health Crisis to help share information and advocate for patients’ rights.

In the play as in real life, Ned (or Larry, whichever) is the one agitating for an official response and emergency funding — first from a negligent City Hall, then taking his frustration all the way to an indifferent Reagan-era Washington. At the same time, Ned falls in love with Felix Turner (Bomer), a New York Times lifestyle reporter who is reluctant to push his journalist colleagues to cover the story.

The more Ned fights, the louder he speaks, the more he alienates his closest allies at GMHC, played here by “The Big Bang Theory’s” Jim Parsons (reprising his role from the 2011 Broadway revival) and Taylor Kitsch.

In some ways, “The Normal Heart” tracks with any number of plays, movies and TV shows that tried to harness the pathos of the AIDS crisis in real time, with various success. Many of those works have since gathered dust.

Not so “The Normal Heart.” Even though it is filled with Kramer’s vintage harangues, the work is still a terrific exploration of what it means to be gay, with or without the disease, whether it’s 1980-something or last Thursday. Kramer’s excoriating tone and abhorrence of the gay closet and cowardice has something to tell us, now and always, about the dangers of looking away.

Nowhere is this more clear than in the moments when “The Normal Heart” lets its characters make the case for their right to be who they most essentially are. Ruffalo nails each and every scene in this regard, particularly when Ned confronts his straight brother (Alfred Molina) about his lifelong disregard of Ned as an equal, the same in every way except one. There’s little “The Normal Heart” can do anymore about AIDS (besides serve as a narrative about how to respond to a public health crisis), but there’s still a very strong dose of medicine here on the subject of equality.

The characters in “The Normal Heart” are all based on people Kramer knew and worked with. Decades later, this fictional narrative, particularly as it comes across in the HBO movie, has taken on some of the qualities of documentary nonfiction. The real history of AIDS is, of course, much broader and more complicated than “The Normal Heart” or any drama could ever hope to encompass. (The film can only acknowledge in its epilogue text that the greater toll from a global AIDS epidemic has been felt in the Third World.) AIDS didn’t happen only in New York, and it didn’t happen only as Kramer saw it.

It’s interesting to watch “The Normal Heart” against the backdrop of another history-making week in the story of gay rights. Oregon and Pennsylvania are the latest states to see their respective bans on same-sex marriage shrivel up in the courts, thanks mainly to a Supreme Court decision last year on the Defense of Marriage Act that opened state laws to constitutional challenges. Nineteen states now permit (or at least don’t prevent) gay marriage, covering nearly half of the U.S. population.

In the way that the story of HIV and AIDS captured the public’s attention slowly but surely in the ’80s, gay marriage also didn’t happen any one particular or dramatic way. Many people who spent decades working for marriage rights took offense last month at a new book by New York Times reporter Jo Becker called “Forcing the Spring: Inside the Fight for Marriage Equality.”

To cover what is arguably the civil rights story of the new century, Becker obtained behind-the-scenes access to plaintiffs’ attempt to take their challenge of California’s Proposition 8 marriage ban to the Supreme Court; with a broad brush, Becker’s book seems to give credit for an entire movement’s success to a select few.

The outrage among some gay activists and pundits that followed the book’s publication was reminiscent of precisely the sort of rants Kramer is known for, about the ways history has been rewritten to exclude gay people and the gay perspective. The urge to both own and shape the historical narrative is a legacy of “The Normal Heart.” Like its creator, it insists on a place up front where it can be heard.

Yet any television watcher surely knows that American history might very well grant credit for gay rights to two fictional men, Cameron Tucker and Mitchell Pritchett, whose long-awaited marriage vows were featured on Wednesday’s finale of ABC’s hit comedy “Modern Family.” The polling data doesn’t lie; since “Modern Family’s” debut in the fall of 2009, the number of adult Americans who are okay with gay marriage soared to a majority, including even the U.S. president, who said that his views on the matter had evolved. Is it really such a stretch to imagine some future historian crediting a sitcom — instead of actual people — with changing perceptions?

Mitch and Cam (played by a gay actor and a straight actor) aren’t anything like Kramer’s visions of an aggressively activist gay community. They’re just the two smiling figurines on the top of a very complicated cake. Their outrage is reserved mainly for domestic disputes and lapses in good taste; their agenda is limited to comic timing.

It’s tempting (but inappropriate) to interrupt the permanent gloom of “The Normal Heart” with the cheerful sloganeering of “It gets better!” and appreciative kisses blown from Mitch and Cam toward everyone who came before. The people Kramer knew and loved and lost — and reconjured as characters for his play and now his movie — remain forever locked in a place of hurt and despair. The happiness and history-making going on today is impossible without them, and they remind us how quickly it can all fall apart.

The Normal Heart (2 hours, 15 minutes) airs Sunday at 9 p.m. on HBO, with encores.