The revelation that Old Steve Rogers was a Skrull would put to rest many of the doubts raised by his presence at the climax of Endgame
The Falcon and the Winter Soldier frequently mentioned the first Captain America, whose presence hovered over the story, but no one would say for sure what happened to him. Even though some fans were enraged by the lack of resolution on whether Steve is living, dead, or on the moon.
The conclusion of Steve Rogers’ story was concluded in Avengers: Endgame by having him return the Infinity Stones to their proper locations in the past and stay there to live the life he always desired. However, this wasn’t very logical. Sam Wilson received the shield from Steve when he returned at the conclusion of Endgame, but might the person standing in for Steve actually be a Skrull?
A crazy theory that Old Man Steve might have been a Skrull has just been put up by a redditor. Everything depends on the star-spangled Avenger choosing to stay in the past with Peggy Carter and living out the years between them in harmony. According to the accepted laws of time travel, doing that would have resulted in the creation of a completely new timeline, which was a rather reckless action.
The MCU’s time travel reasoning has received a lot of criticism for being inconsistent, which has led to debate among fans and several theories for how old man Steve may have come back.
According to the theory, the errors in his sudden reappearance in the climax of Avengers: Endgame would be clarified by a Skrull playing in a different capacity, either a good one filling in and acting on behalf of Nick Fury to push Sam Wilson closer to the shield, or a villainous one acting in their own self-interests in the lead-up to Secret Invasion by altering the very fabric of time to make sure it ended up in the possession of John Walker.
The old Captain America from Avengers: Endgame turning out to be a Skrull would be a great way to fix that plot inconsistency, connecting the aspect of the Infinity Saga with the MCU’s future plans.