According to Russo, that the line is shocking and unexpected coming from Captain America is the whole point — not just of the moment itself, but also of Avengers: Endgame as a complete entity. Steve’s profanity-punctuated remark represents what Endgame is all about: doing the unexpected. This includes having Steve swear, for certain, but it goes beyond that in a major way.
Russo explained that the line is also a “misdirect on what the mission is going to be.” Fans are led to believe, upon hearing the line and seeing the action card that pops up on screen thereafter, that “the movie is going to be a space movie” — that the Avengers are going to be hoping around the cosmos, tracking down Thanos and trying to defeat him.
However, as Russo noted, “ten minutes later, it’s different.” After Thor slices Thanos’ head off when it’s revealed that the Mad Titan obliterated the Infinity Stones into atoms, rendering them completely irreparable and the Avengers’ plan totally ruined, Avengers: Endgame takes a turn. The action jumps ahead five years, where many are consumed with grief over the events of Infinity War and hopelessness over the fact that the Stones have been destroyed, and eventually sees the Avengers attempting a whole new plan: split up into groups, travel through time, snag the Infinity Stones from several places in the past, power their own Infinity Gauntlet, and use it to undo Thanos’ snap. Pretty different from what you expected to go down the first time you saw Endgame, huh?
As Russo put it, the “mission with Endgame” was always to “subvert expectations throughout the film and keep surprising you.” Cap’s comment itself and the way it prepares viewers for a plot that doesn’t end up playing out as anticipated encapsulates that perfectly.
Written by: Looper