It’s one of the best scenes in Avengers: Endgame -- when Thanos has Thor pinned against a rock, and all hope seems lost for the God of Thunder until Steve Rogers picks up and wields Mjolnir, proving he is worthy as Captain America. It is an electric moment in the theater, and there are countless recordings of fans cheering at the incredible moment. In fact, it's arguably one of the greatest moments in the Marvel Cinematic Universe.
But fans know it wasn’t the first time Rogers tried to pick up Thor’s famous hammer. In Avengers: Age of Ultron, there is a charming scene where the Avengers challenge each other to pick up Mjolnir. Thor is extremely cocky and convinced none of them are able to do it. And indeed, most of them can’t, except Cap.
In a hilarious bit, Cap nudges Mjolnir a tiny amount before conceding the competition and admitting to being unable to move the hammer. The motion is enough to make Thor panic before he regains his confidence as Rogers admits defeat. But it got left deliberately vague as a fun little Easter egg for fans over whether Rogers was actually able to lift the hammer.
However, in 2019, the Russos seemed to confirm that Rogers was always worthy to lift the hammer. He simply chose not to at that moment out of respect for Thor and not wanting to upset him. But while it's pretty clear from Thor’s comic reactions in that scene, it might be worth disagreeing with the Russos on this front. While Rogers may always have been worthy to wield Mjolnir, he was not worthy to wield it at that moment for one specific reason.
Rogers was not worthy to lift Mjolnir at the party because he was trying to do it for selfish reasons. It was for a harmless competition, but a competition nonetheless. The hammer moved slightly to hint that he was worthy in character but was not worthy to lift it at that moment.
The idea that Steve Rogers had to grow into being worthy to lift Mjolnir is far more interesting than simply suggesting that he was always able to wield the hammer. While Rogers is a hero, he isn’t perfect, and it’s better when these imperfections get worked into the character and his journey. And a version of Cap who earns his worthiness is more interesting than a version that's simply always worthy.