But if Steve goes into a new timeline only to go Full Cap and prevent all the horrors he knows are coming.......well, that ain't exactly living. Which is what our guy Steve set out to do.
I admit, I can't get around the idea of reality creation as some benign side effect of time travel. And the idea that new timelines are a ginormous problem is a stand I share with both the Ancient One and Mordu. Steve opting to live a non superhero life in our past seems more reasonable to me than his choosing to create an entire new reality in which he can shag Margaret. And then somehow cross over into the original reality to hand Sam a shield.
Until I see or hear otherwise, I'm going with the idea that our Time Heisters put everything back where it belongs. And after Loki puts the space stone back, no new time lines will be created.
See... I don't consider consigning Steve to decades and decades of mental anguish, angst and torture to be "living" myself.
Your supposition, and it's not an out there position, is that Steve made a decision to retire after the battle with Thanos and the sacrifice of Tony Stark and used the mission to return the stones and the hammer as cover. He lives his whole life secretly in the background of the MCU and appears at the right moment to hand a newly created shield to Sam and pass the role of Captain America off to him.
My issue with your take is that, once more, the film goes to great lengths to explain the mechanism of time travel to the audience and the above doesn't fit the film's time travel explanation. Second, this interpretation hinges on an interesting take, though not totally unfounded, on Steve Rogers' personality, character and moral compass. Now I do get to a degree where you are coming from. What you are supposing is that Cap WOULD have the moral fiber to not intervene during those decades and decades so as not to mess with the flow of events. I get that as a legit view of Cap. It's easy to think of him from the view that given the stakes he would hold fast for "the greater good".
But... I would call that a formula for the worst possible way for Cap to have lived from 1946 to 2023. And also one which would make him at best either a distant partner to Peggy or a embittered and perhaps even emasculated feeling one. I can suppose that Cap would balance out the need for action against the greater good of the ultimate flow of events in the timeline... But I don't see that as the absolute and only way this would or could affect him. This set of circumstances is a bit different than say some other scenario of his retirement and putting the shield down for good. As and example, say he instead stays in 2023 and goes off into the sunset with Sharon Carter (However one feels about the character, who seems radioactive for reasons that baffle the **** out of me around the Hype... Just go with this.) and, I don't know... He asks Black Panther to build a new shield and hands it off to Sam, same as before and now he's your "Citizen Steve" only still youthful and in the post AEG/2023 timeline. Now there will be more tragic and momentous events to come of course. Both in terms of fiction, this is a super hero universe after all, as well as in real life. Now retired Steve in this set up just has to accept that he's moved on, and he has to console himself at least partially I think with the idea that he'll never know what he could have done to prevent certain events. He's the gunslinger that's hung up his guns.
But your scenario doesn't even give him that out. Going back in time and having to stay anonymous in the flow of history for the sake of not ruining the timeline is more than just an exercise in some kind of objective morality. This isn't like being retired in a post 2023 world and WONDERING about what one could do in the face or tragedy and emergency. This is absolutely knowing to your core that you alone in all the world with your foreknowledge have the answer to untold amounts of suffering. To be perhaps overly dramatic this is me having the full knowledge of the Sept. the 11th terrorist attacks, doing nothing about them and then walking around Ground Zero in lower Manhattan a year or two years later and looking into the eyes of every person that lost a loved one that day. This would be the equivalent of me having that information, not using it and then having to pass U.S. veterans maimed or mentally unbalanced because of their experiences in the foreign military operations that launched because of the attacks. This is thinking of the civilian deaths in those foreign countries which were consequences of the Al-Qaeda attacks of 2001. It's all that and decades more... And instead of it being regular guy ME, instead it's Steve Rogers, Captain Freaking America. A man burdened now not only with the very specific knowledge of what will happen and how to stop it but one almost uniquely equipped to be the man to actually do something about these events. Only... He can't.
That's mind-**** city in my opinon. Even if he comes to terms with that and accepts it all, on some level he's still going to be emotionally affected by this. And not just something that you can get over in the span of some years. This is something that would hang over him for 70 plus years.
That's consigning Steve to a living hell in my opinion. That's forcing Peggy to have to live with either a very angry or bitter person or a person that will forever be unsure of his decision to be with her. None of this is a good formula for a happy marriage.
And once more... None of it is even necessary to even consider given that AEG lays out that Cap can indeed time travel, live with Peggy and not have to worry about the repercussions of his actions on the time and place he came from or any of his friends' lives due to how the film more than once lays out it's temporal transportation mechanics.
