"Avengers: Infinity War" isn't for everybody. Specifically, it's not for anybody who hasn't watched pretty much every other movie in the Marvel Cinematic Universe.
That's because pieces of the story have been developing over the past decade, reaching all the way back to 2008's "Iron Man." Thanos, the universe-wrecking big bad of "Infinity War," has been teased since "The Avengers" back in 2012, and slowly bits of his story have made their way into other movies, like "Thor: The Dark World" in 2013, "Guardians of the Galaxy" in 2014, and "Avengers: Age of Ultron" in 2015.
Most of the other MCU stories have been gradually building toward the arrival of Thanos (Josh Brolin), teasing what a big deal it is while also developing the many heroes who became a part of it. "Infinity War" is less like the third installment in the "Avengers" movie franchise, and more like the end of a 10-year season of an MCU TV show. It brings together everything that's happened before it, bringing all the characters together to deal with a new adversary.
That's kicked up some criticism of the movie. The New Yorker's review in particular takes issue with the "Infinity War" approach by calling it "a two-and-a-half-hour ad" for every other movie in the MCU. It complains that characters aren't introduced, they just show up, and the movie expects you to know who they are and what their deal is.
What this line of criticism doesn't seem to take into account is that characters not being introduced and the movie expecting the audience to remember information from other entries is not a bug. It's a feature. Not bringing along people who haven't seen almost every other MCU movie is not a failing of "Infinity War," because the movie isn't made for those people. It's made specifically for MCU fans, and it's okay with anyone else skipping it altogether.
The cynical view of Marvel's shared universe approach to its movies is that they all exist to advertise the one another, specifically thanks to the now-ubiquitous post-credits coda scenes Marvel Studios includes with each of their installments. At some point, that view was probably correct, before the stories started to gel. Today, however, the best part of the MCU is that Marvel is willing to trust its directors, writers and cast to use all those stories to build toward something more. The season of a TV series analogy is still apt -- each movie is building on the foundation laid by the last, creating a season-long arc for characters and stories.
That's the reason "Captain America: Civil War" is still among the best of the MCU movies: not because it expects you to know everything about Tony Stark (Robert Downey Jr.), Steve Rogers (Chris Evans) and the Avengers crew, but because it rewards you if you do. "Civil War" explores the different personalities and motivations of its characters, built up through their experiences across multiple movies -- in the cases of Cap and Iron Man, as many as five previous stories. If you've been invested in Tony Stark through his various movies, then you know by the time you hit "Civil War" that he doesn't really trust himself to take care of the world as a superhero. Meanwhile, if you've followed Captain America's stories, you know he feels he can't trust anyone else to. The best part is that so many movies have given these characters a chance to grow and change, something "Civil War" can exploit to create and deal with interpersonal conflicts that otherwise wouldn't be possible.
"Avengers: Infinity War" is the same way. It's not meant to punish the people who haven't kept up with the MCU up until now. It's meant to reward the people who have. The MCU is taking the cool idea of the comic crossover, in which lots of characters' stories weave together into a bigger event, without the confusion of running all those stories in parallel. There are handful of movies to see every year or so; it's not exactly an insurmountable feat to keep up.
And sure, it's true that the MCU doesn't function like other blockbuster movie series. It's more of a brand than a franchise, and pulling in all those various threads from a number of series is more demanding than almost every other moviegoing experience. But then again, it's easy enough to opt out. It's fine to pick and choose the MCU movies you're into and skip the ones you're not (July's "Ant-Man and the Wasp" is a heist comedy that seems largely uninvolved with "Infinity War," so there you go). There's no requirement to go into the big crossover event if you're not up to speed, and similarly, there's been no shortage of warning that this is, in fact, a big crossover event, and if you want to see it, you should be up to speed.
"Avengers: Infinity War" is not an ad for the MCU, it's proof that the MCU can be worth all this investment on the part of the audience. It's end result of time and attention spent. That it doesn't cater to the casual fan might be off-putting, but there are lots of other movie series and blockbuster franchises that do. Critics are welcome to the cynical view that Marvel has created a giant, self-sustaining ticket-selling machine. The truth is also, though, that Marvel's successful MCU experiment sells tickets because it supplies something that doesn't exist anywhere else in movies: TV series-like investment, with series finale-like payoff.