As this is a movie review, plot points from the movie will be discussed below. (Who lives and who dies is not addressed, however.) Taking a cue from Thanos, I will wipe out half of all the people who read beyond this point and then complain about spoilers.
If Marvel had any guts, they would've called this movie Thanos and made it like a straightforward superhero origin story in the mold of Iron Man or Thor or Ant-Man or any of the others. Every emotional beat belongs to Thanos (Josh Brolin), every piece of the action is driven by his effort to complete the Infinity Gauntlet (a glove that allows him to channel the power of the Infinity Stones), every effort in the movie is undertaken to move him one step closer to eliminating half of the universe.
Instead of Thanos, however, we get Avengers: Infinity Characters. Instead of focusing on what turns a man into a monster—turns out that the big purple galoot's planet, Titan, was destroyed as a result of resource depletion and that his suggestion to save their people by eliminating half of Titan's population was dismissed as cruel—we spend time with Tony Stark (Robert Downey Jr.) and Pepper Potts (Gwyneth Paltrow) as they blather on about having kids. Instead of lingering on the twisted relationship between Thanos, Gamora (Zoe Saldana), and Nebula (Karen Gillan), the only emotional arc from the rest of the Marvel movies to pay off in this one,* we have to slog through the feelings of the Scarlet Witch (Elizabeth Olsen) and Vision (Paul Bettany), minor characters we've barely seen in previous films about whose relationship we could not care less. Instead of really muddling through the ethics of Thanos's Malthusian plot, we spend A TON of time watching Thor (Chris Hemsworth) make an axe.
An axe.
Probably, I dunno, 15 minutes of this 150-some minute effort deals with Thor trying to forge a weapon. I mean, it's a pretty cool axe, I guess! Made via the heat of a neutron star for some reason! And it's neat when the blonde-haired, blue-eyed Norse god shows up out of the blue to save the technologically hyper-advanced African nation of Wakanda with, again, an axe.**
But still. It's just an axe, and a distraction from the more interesting Thanos-centered action that functions as a handy emblem for everything that's wrong with this flick.
Avengers: Infinity War is very much a movie from the Marvel Cinematic Universe: the characters banter and quip; the action scenes are put together with basic competence but little virtuosity; the story keeps moving. It is never boring, exactly, but it is often underwhelming in part due to the fact that it is trying so hard to overwhelm, to flood the screen with characters and action and death and destruction and mayhem. And there's an end-credits scene!
Describing the plot is foolishness—there are roughly 872 subplots, few of which resonate particularly strongly, all of which seem to be little more than an excuse to stitch together action sequences—except to say that it revolves around the efforts of Thanos to wipe out half the universe. Which brings me back to my main frustration with the film: everything about Thanos is good! The character design is solid (he's basically a purple hulk, but smart and well spoken) and Josh Brolin does surprisingly tender work under all that CGI. (Let the quality of his performance serve as a lesson to people who write about films and acting based on a movie's trailer.) His plan and his reasoning for it are both ludicrous—he's basically an intergalactic Paul Ehrlich, and Paul Ehrlich is a charlatan who should've been laughed out of polite society eons ago—but there is, at least, some logic behind it, a core to his madness.
As the culmination of ten years of Marvel movies, fans will likely find Avengers: Infinity War satisfactory. As a piece of narrative filmmaking, however, it's a disaster: a bloated monstrosity that smothers to death its most intriguing aspects.
*As an aside, Infinity War is a much, much better Guardians of the Galaxy movie than it is an Avengers movie. The Thanos-Gamora-Nebula-Quill (Chris Pratt) relationship is the only thing that's actually interesting in the whole picture.
**The think pieces regarding this plot point are, as the kids say, going to be "lit af."