Well the obvious time paradox would prevent them from taking this approach. By destroying their own future they would never come back to save it.
There must be another explanation.
There must be another explanation.
Likewise, if you travel back in time and change the future, you're not helping the people in the future you left, you're helping the people in the past avoid that future. But to you, it looks the same. It looks just like the past you're familiar with, and it develops into some semblance of the future you were expecting. So for all intents and purposes, from a subjective viewpoint you're avoiding the paradox and helping your ancestors. It doesn't matter if the people you left are still suffering, subjectively they don't exist anymore.
Sounds like what you are saying.
He leaves his friends behind in a world where WW3 breaks out over world powers fighting over research for a working time machine. In a way, he is leaving his friends to die in a post-apocalyptic WW3...but that doesn't matter because he's saving them in his 'current' timeline. The other worlds, from his perspective, "don't exist" anymore.
>In all actuality, "you" died and another "you" took your place. But to you and everyone around you, it seems like nothing has changed, so you carry on with your life.
In the show they call this power "Reading Steiner" when he "replaces himself" in a new timeline. Since he is capable of remembering what happened in the other timelines (nobody else does - as from their perspective these other timelines never existed).
Time travel is fun to think about. :P
My point really, is that there are varying fictional universes but in ours, we don't currently have a way to do teleportation. So, as you say, experience is subjective.
If you jump back into the old universe, nothing will have changed – so that is pretty much the only place you should stay away from.
There won't be a future where people knowingly will have experienced the results of your heroic deeds, which might be sad to some, but you can just tell/try to convince them of what good you did. Maybe take some videos or other proof.
That said, you do lose the drama surrounding the possibility of "destroying the future" via making gross (killing Hitler) or subtle ("butterfly effect") changes, as none of the consequences ever affect the universe you travelled from (other than the fact that you've left, never to return).