The Marvel Cinematic Universe doesn’t require the same suspension of disbelief as most superhero movies. First of all, the scope of the MCU allows us to get a closer look at things like SHIELD, explaining how certain supernatural/superpowered phenomena have stayed secret for so long. The SHIELD characters also show how normal humans react to the sudden appearance of people like Thor and Captain America. Secondly, the hero/villain conflicts in the MCU are not confined to just the hero and the villain, but have a solid foundation in the world “outside.” Even Malekith in Thor: The Dark World (probably the most two-dimensional villain so far) was shown in terms of the real consequences of his actions, with that tear-jerking Asgardian funeral scene.

Most importantly of all, the everyday human characters in the MCU are just as significant and powerful as the superpowered characters. Nick Fury is undoubtedly more powerful than any of the Avengers: he’s their boss. Peggy Carter and Howard Stark helped found SHIELD, an organization that spent decades shaping the way the world would react to people like Thor and Iron Man. Pepper Potts and Jane Foster both have an ongoing impact on the world around them. Phil Coulson is the catalyst that brings the Avengers together in the first place.

In CATWS, we see that concept expanded to its greatest extent so far, with Agent 13 and crowds of other SHIELD agents making the decision to ignore their orders and fight alongside Cap. By elevating the importance of human/civilian characters, the MCU creates a far more complex and believable world than most other superhero movies — and all without disempowering its heroes.

— Captain America: The Winter Soldier, and its impact on worldbuilding in the MCU.