The movie opens with grad student Kate Dibiasky (Jennifer Lawrence) discovering a new comet. With the help of professor Randall Mindy (Leonardo DiCaprio) they discover that this comet will strike Earth in six months and cause an extinction-level event. This takes them to the White House, where they're brushed off and silenced. They do some talk shows, where they're humoured and doubted.
This being a satire, everyone is a bit over-the-top. As several reviews have said, this is heavy-handed, but also dead-on on denial of facts, the denial of science, political scandals, and rampant corporatism.
What a list of names: DiCaprio, Lawrence, Jonah Hill, Timothée Chalamet, Ron Perlman, Ariana Grande, Cate Blanchett, Meryl Streep. The cinematography is occasionally very weird, hopping from topic to disconnected topic very quickly - I assume to show us life happening across the planet, but they did this many times. Mark Rylance does almost exactly the same character as in "Ready Player One," except with a slightly better haircut. He's a darling with the critics right now, but I haven't seen it yet (yes, I know I haven't seen the acclaimed performances).
I found the movie reminiscent of (at least) "Last Night" and "Seeking a Friend for the End of the World" - "Last Night" faces an unexplained apocalypse, but "Seeking ..." is brought about by an asteroid hurtling toward Earth. Being both middle-aged and a fan of Science Fiction I've probably seen more end-of-the-world movies than most people, so many people won't have seen as many of the antecedents.
It was depressing, but also funny and fascinating as they trotted out ever-more-awful unexpected outcomes.