Over the past few decades we've gotten used to the idea of movie, TV, and other media franchises undergoing total reboots, with the creators breaking continuity with the original series to create new stories using the same core concepts and characters. It's pretty much taken for granted that whenever a new team takes over one of the non-MCU superheroes, like Spider-Man or Batman, that the new movies will have nothing to do with any of the previous onscreen iterations. Likewise, Ron Moore's Battlestar Galactica uses the same story and some of the characters from the 1978-79 ABC series, but it differs significantly in tone, style, and themes. And there are even hybrids that combine seeming reboots with established continuity, like the Abrams Star Trek movies or Days of Future Past, which are tied to the classic Trek shows and films, but take place in a timeline running parallel to the original universe, a concept that arguably dates back to the comic book multiverses of DC and later Marvel.
But what about "soft reboots" — movies or shows that take place in the original universe, but strategically ignore or downplay previous stories to push the franchise in a different direction without radically violating "established" continuity? The reboots can do this in a number of ways — by altering the style, introducing new major characters, or introducing new concepts to the core mythology that subtly — or radically — alter what the franchise is supposed to be about. On TV, Doctor Who is arguably the best exemplar of this approach — the cast, including the lead, turns over every few years, and often the format shifts as well. But it's also an example of a franchise whose mythology was built from the ground up, as most of the core concepts were established only after years — or even decades — of episodes, many of them developed by different writers.