I was reading something (folks who know me can guess, but I shan't spoil) that had a spot of time travel in it, and, of course, changing the past wrecks the present. I have always been struck by how consistent it is that efforts to change the past always produce a worse time-line. It is almost as if the time-line we are in is the best one of all, and that every other one is inferior. This is some hubris, fellow Earth-1/Earth-prime/whatever-we-want-to-call-ourselves. Perhaps one of the best visualizations of alternate timelines was the episode of Community.
Sure, there are some very few exceptions: Quantum Leap was is the primary exception as Sam's efforts to change the past generally worked out, improving people's lives without breaking the space time continuum in any major way. Back to the Future is another example, but one with plenty of warnings about how much more damage can be done than fixing. The fixing here is mostly to un-do the damage but turns out, by accident rather than by intent, to produce a better present--Marty's parents are cooler and more successful in the revised 1985.
Mostly, however, efforts to change the past lead to utter heartbreak. I remember reading a Marvel series "What If?" which would ponder basic questions of the Marvel Universe and always, always, always the lesson would be that if that event was changed--Gwen Stacy dying, the death of Phoenix, etc--the new reality would be much worse.
This smug attitude about the "real" time-line seems problematic. Sure, it is fun for writers/filmmakers to set things up this way since doing otherwise would mean that our reality is inferior. That probably does not sell books or tickets. But it does represent some arrogance to suggest that the current timeline is the best possible one, does it not?