8 Awkward MCU Moments That Must Have Happened Off-Screen
6. Captain America Returns The Infinity Stones - Avengers: Endgame
The only reason Bruce Banner was allowed to take the Time Stone from the Ancient One was because he promised all six stones would all be returned to where they were taken from when all was said and done. Steve Rogers was sent to do this job at the conclusion of Endgame.
Returning the Power Stone to Morag would have been relatively simple, as would the Time Stone, as The Ancient One would have been expecting him. Cap could have disguised himself as his past self to return the Mind and Space Stones to SHIELD in 2012, but the remaining two would have caused a bit more of a problem.
The Soul Stone was given to Clint as part of an everlasting exchange for the soul of Natasha Romanoff. Everlasting being the key word. How was it even possible to undo such a thing, and how would Steve have reacted to seeing the Red Skull again?
Arguably the Aether would have been, not necessarily more difficult, but certainly more awkward. The details are sketchy on how Rocket was able to extract the Reality Stone from Jane Foster in the first place, but trying to get it back inside her would have potentially been even worse.