The following contains spoilers for Spider-Man: Homecoming
It was the end of March and the second trailer for Spider-Man: Homecoming was released online. It was the most significant look we'd had at the new film with about two and half minutes of content. It was a great trailer, but there was a problem, it really looked like it gave away the whole plotline of the film. Now, the movie is out in theaters and fans are discovering two things. First, yeah, it pretty much does tell the entire Spider-Man/Vulture storyline. Second, it really doesn't give away the movie at all.
Here's the basic rundown of Spider-Man: Homecoming according to that trailer. Peter Parker wants to be an Avenger. Tony Stark tells him to slow down and be a "friendly, neighborhood, Spider-Man." To that end, Peter does his best to make New York City a better place from a ground level perspective. Then, he stops an ATM robbery by some criminals with some really major firepower they shouldn't have. Tony Stark tells Peter not to worry about that, or the flying Vulture that he has a run-in with, but Spider-Man continues his investigation and ends up on a ferry which very nearly sinks, killing everybody, until Iron Man arrives to save the day. Tony takes the suit away from Peter for his rash actions, but Peter feels a need to redeem himself so he puts on his old suit and confronts the mastermind, leading to a final confrontation.
Yeah, that's pretty much what happens. At the same time, it has nothing to do with what's important in Spider-Man: Homecoming.
The trailer absolutely does lay out the superhero arc of Spider-Man, and it doesn't leave anything of significance out. Most of the important details are there, even if missing context doesn't make them perfectly clear. But, as it turns out, the reason the trailer showed us so much of this, is because they were hiding what the story is really all about.
As great as Spider-Man is in Homecoming, the movie is about Peter Parker. It's about him trying to find his place in the world while occupying a completely unique place in that world. Make no mistake, while we never see a single radioactive spider anywhere in the film, this movie is absolutely an origin story, in that it follows Peter Parker as he learns what it means to be a hero. The words "with great power comes great responsibility" are never spoken, but that lesson is very clearly learned.
What's important about Spider-Man: Homecoming isn't that he fights and beats a supervillain, we all knew that was going to happen. What Spider-Man: Homecoming does do right, is all the little details that don't make for great trailer moments. In fact, because the movie skips past the spider bite it gets to spend more time dealing with the "learning how to be Spider-Man" part than any previous movie. Sometimes that takes a humorous bent, such as how does one navigate when there is nothing to attach a spider web too, sometimes it's more serious, such as the moment that immediately precedes Spider-Man's final battle with Adrian Toombs.
In addition, the fact that this Peter Parker is still in high school is important to the character, so it's important to the movie. What parts of Peter's high school experience were in that trailer? You likely can't name much, that's because they're not really in the trailer, so you saw them on screen for the first time. It's these moments that tell you the sort of person that Peter Parker is, without them, the finale of the film has no real meaning. It's just a generic superhero fight, and we've seen plenty of those. Spider-Man: Homecoming is better than that precisely because there's more to the story than the superhero vs. bad guy dynamic.
In the end, most of could have probably guessed at the Spider-Man: Homecoming plot a year ago and been right more often then we were wrong. "Spider-Man wins" is about as big a spoiler as the Titanic sinks at the end, but what's important to a movie is the journey, and until you've been on it, you don't really know what this movie has in store.