One of the most satisfying moments in the entire MCU occurred near the end of Avengers: Endgame, when Captain America proved himself worthy of picking up Thor's enchanted hammer Mjolnir and then proceeded to use the godly weapon to inflict major damage on Thanos. Now, in the recently-released book Marvel's Avengers: Endgame - The Art of the Movie Marvel, studio executive Louis D'Esposito has revealed that the Captain was always capable of lifting the hammer.
"I think one of the most special moments in this film is when Captain America picks up Mjolnir, If you remember from Ultron, they were all sitting around in the Avengers complex in Manhattan, and there's a party, and they're all a bit inebriated, and they're loose, and they're having fun, and they're all trying to pick up the hammer. It's Captain America's turn to try, and you look over to Thor's face, and he says, 'I think he might be able to do it,' but Cap doesn't pick it up. But Cap could've always picked it up. He didn't want to at that point because it would've not been right."
The theory holds in good faith with what fans had suspected for a long time: That Captain America, who only managed to nudge the hammer a little in Age of Ultron, far from being unworthy of lifting it at the time, was only pretending to not be able to lift it out of respect for Thor's claim over the weapon bequeathed to him by his father.
Wielding the hammer was a big deal for Thor at that time, since his entire first movie was devoted to him becoming worthy of lifting the hammer. For Cap to then casually lift it on his first try would be like stealing the thunder from the literal God of Thunder, and we all know Steve Rogers is too good of a guy to do that to a friend.
When Cap does finally lift Mjolnir, it becomes symbolic of him completing his journey, and going from being a superhero to transforming into a warrior out of myths and legends, wielding a weapon that stories are written about, to defeat a monster from another world in a cataclysmic battle for the fate of all of existence.
It's the same kind of exhilaration audiences felt upon seeing King Arthur draw Excalibur from the stone, or Harry Potter lay claim over the Elder Wand in the final moments of his battle with Lord Voldemort. Any other moment in the past where Cap could have revealed himself worthy of Mjolnir would not possibly have had the same impact.
Of course, it does call into question the end of Age of Ultron, where we see Cap and Tony more than a little disturbed to know Vision was capable of lifting the hammer. The two can be seen arguing with Thor about the conditions for a human to lift the hammer, and the scene makes it clear that Captain America was genuinely disappointed at his own inability to lift the hammer. Obviously, this is a case of the studio putting a new interpretation on a previous moment in the franchise to make it fit better with fresh developments in later films. But hey, Marvel fans sure aren't complaining. ComicBook.com