Adam McKay made his mark behind the camera for Will Ferrell’s greatest comic hits — “Anchorman,” “Step Brothers” etc. But with “The Big Short,” an all-star romp that explained and sent up the shortsighted Wall Street types who wrecked the economy in 2007-8, we had to start taking him more seriously. He has insights into the culture, politics and American Way that are worth hearing out, and he isn’t shy about rendering his civics (“Vice”) or economics lessons in farces.

“Don’t Look Up” shows us he’s been reading his glowing reviews a little too eagerly.

It’s an another all-star comedy, with Oscar winners Leonardo DiCaprio, Jennifer Lawrence, Meryl Streep, Cate Blanchett and Mark Rylance in its ranks. It’s a satire about a Big Subject — the ways nothing gets done in the face of great planetary crises thanks to money, know-nothing politics and a shallow, ignorant and easily-distracted culture that can’t focus on anything big because trivia, optics and “clicks” control our attention spans.

McKay’s just as “right” about his target as ever. But the tone of this “Deep Impact/Wag the Dog” mashup is off. It veers towards strident, and as the clutter gathers around it, it drifts into dull. The jokes dry up and only a few members of his cast are veterans of “let’s make this funnier on the set” filmmaking.

Yes, Jonah Hill’s the funniest player in it, but Blanchett and Streep — thoroughbreds in any genre — give him a run for his money.

A beautifully-conceived first act mimics the openings of “Armageddon” and “Deep Impact.” Kate (Lawrence), a solitary Phd candidate in astronomy, sees something during her telescope session, charts it through a few frames, and lets out a little squeal of delight. The observatory fills with classmates and their nurturing professor, Dr. Mindy (DiCaprio) and they celebrate Comet Dibiaski, named after Kate of course.

Then Dr. Mindy leads the class through the flight path math, and he stops short. He sends everybody home as he and Kate have their first freak out. It’s heading towards Earth, and it’s big.

McKay’s homework shines in the scenes that follow. Mindy and Kate have to reach out from their Michigan State U. lab (a top-ranked astronomy school), get confirmation from a Subaru telescope (yes, the car-maker sponsors telescopes worldwide) and get the head of the Planetary Defense Coordination Office (“A real place” a screen title reminds us) on the phone.

Dr. Teddy Ogelthorpe (Rob Morgan, having a Netflix December) is no-nonsense, “extinction level event” alert and let’s “schedule the school field trip (get our scientists to the White House)” and break the “planet killer” news to the president.

Kate needs a moment. “I gotta go get high.”

That should set the tone for the rest of the movie, with the science folk, not-used-to-dealing-with-politicians or uneducated laymen or TV chat show ditzes, hurled into a White House where everybody’s on a different power trip, especially the president’s shallow chief-of-staff. He (Hill) also happens to be her son.

“Thanks for dressing up” is the lightest of his insults to the disheveled scientists.

Streep plays a president obsessed with optics, a “troubled” Supreme Court appointment and sinking poll numbers, fretting about “If this breaks before the mid-terms, we’ll lose Congress.”

That’s McKay’s first misstep. Common “Wag the Dog” sense tells us that this is precisely the “change-the-subject/rally-the-nation” distraction President Orlean needs. How’d she miss that? Oh. Right. TFG.

“They’re not even smart enough to be as evil as you’re giving them the credit for,” Kate decides, at one point.

It takes a while for our Palin-meets-Hillary president to come around, with Dr. Mindy staring in slack-jawed disbelief at her “sit tight and assess” brush off, and anger-mis-manager Kate flipping the “Are you f—–g KIDDING me?” out. They have to go to the press and meltdown on a chat show that is the meanest takedown of Michael Strahan and Mika Brzezinski (Tyler Perry and Blanchett) you could imagine. He’s bubbly and dizzy, she’s even shallower and hot-to-trot. “On our next show…”

“Don’t Look Up” points us towards the technological “options” we hear about with every asteroid “near miss,” but filters them through American politics and the fizzy dreams and schemes of a cellphone billionaire (Mark Rylance, with bleached teeth, channeling Joe Biden’s impersonation of Musk-Bezos-erberg).

In other words, don’t get your hopes up.

The bulk of the movie is a blend of spot-on take-downs — President Orlean’s stage-managed, spectacle-packed grave TV announcement that plays like a send-up of an infamous “Mission: Accomplished” moment — and meandering distractions.

We see the ways the “message” is mishandled by “The Media,” leaving the door open to crackpots, every one of whom has a YouTube/Instagram megaphone to scream lies and sew doubt.

Some supporting players score big. Ariana Grande plays a self-absorbed pop starlet whose break-up and make-up with another pop star is a global distraction. But let her be the first to jump on the “Look up and see for yourself” vs the “Don’t Look Up” science-denying nutoisie and she’ll write you a hit to publicize it.

Chris Evans plays a movie star whose latest film is timed to capitalize on the day of the collision, Himesh Patel is Kate’s online “journalist” beau who instantly sells her out and goes for an “I Slept with a Lunatic” book deal. Look for Patti Lupone in the frequent montages of TV/social media coverage as a gum-snapping rube selling shovels online “because we gotta dig in.”

And Ron Perlman shows up as an unfiltered, mercenary “American hero” badass selected to fly a re-commissioned space shuttle into the comet to blow it up. He’s at his bellowing, blustery best here.

There’s no point in adding Timothee Chalamet as a dopey Sk8er Boi who comforts Kate after she’s become a meme and the most hated woman in America, thanks to her on-camera meltdowns and the comet that bears her name.

McKay nails the life-cycle of “scandal” and “emergency” in American public life, skewers a lot of easy targets and loses the thread more often than he should. But dark comedies like this are hard to pull off because if you lose your nerve, it’s just a joke, and if you don’t, your movie sinks into despair.

DuckDuckGo the phrase “movie satires” and you’ll see a few examples that worked, and scores and scores that never had a chance.

Opening with “Network,” stumbling into “War Machine” but ending “On the Beach” just doesn’t play, making this a morose misstep for a filmmaker who was on quite a roll.

Rating: R, Language Throughout (profanity), Graphic Nudity, Drug Content, some Sexual Content

Cast: Leonardo DiCaprio, Jennifer Lawrence, Rob Morgan, Meryl Streep, Tyler Perry, Timothee Chalamet, Jonah Hill, Mark Rylance, Ariana Grande, Cate Blanchett and Ron Perlman

Credits: Scripted and directed by Adam McKay. A Netflix release.

Running time: 2:18