Wrapping up eleven years and twenty one movies' worth of storytelling, Avengers: Endgame has a heavy burden to bear. But since most of its plot was carefully seeded across at least half of the preceding "Marvel Cinematic Universe" installments, one gets the notion that Marvel head honcho Kevin Feige knew his saga's, uh, endgame years ago, which is why everything in this film feels like it's falling neatly into place, rather than being awkwardly crammed into a bunch of plot holes (like, say, the Star Wars prequels).
When we last saw our protagonists at the end of Infinity War, the equity-obsessed villain Thanos (Josh Brolin, motion-captured) had acquired the six powerful Infinity Stones, snapped his fingers, and killed off exactly one half of all living creatures throughout the universe. As any well-versed moviegoer might expect, the surviving Avengers must resort to time travel in order to undo Thanos's fatal decision, or else we'd have several Marvel movie franchises dead in the water. To Endgame's credit, it takes our heroes a full five years to figure out how to do this. In the meantime, in the movie's finest touch, they have moved on from the tragedy in different and often hilarious ways.
Endgame is very much a gift to the devoted fans who showed up for all (or most) of the previous 21 films. To wit: after the Avengers debate the logistics of time travel – their only reference point being the same time travel movies that the rest of us grew up with – the story takes a page from the Back to the Future Part II playbook and sends our heroes back into key scenes from previous films, in order to pilfer the Infinity Stones from the past. (Coincidentally, Endgame is scored by BTTF composer Alan Silvestri.) Thus seemingly every major actor from earlier MCU films turns up for a cameo.
Avengers: Endgame is both epic and intimate, funny and touching, clever and hackneyed. By and large, it satisfies. A few scenes feel overly calculated to get the audience cheering, and too many favorite characters pop up for just half a minute of derring-do, only to retreat into the background. (So it must be, when you have such a huge cast.) I'm still impressed that Feige, the Russos, and screenwriters Christopher Markus and Stephen McFreely would choose to fill their finale with more quiet human moments than bombastic battle sequences, but it only shows their understanding of why audiences love the MCU in the first place: it's the characters, stupid.