Time travel is not a good thing and can also lead to really bad storytelling if you really put too much thought into the idea. For something like Doctor Who, where history is simply a place to visit, it can be fine. But the more you dig into the mechanics the worse it gets. (See my review of Godzilla Vs. King Ghidorah for example.) But if your story involves altering history you’ve just tossed yourself down the rabbit hole. Author James Harrington explains why he avoids time travel stories and it’s why I really wouldn’t want to tell one, either.