Hello, there! I have to write a paper on Doctor Who for a class of mine and I figured this would be a good place to ask a question pertaining to my efforts:
What do you folks consider to be the most notable moments of change within the Doctor Who property?
Any circumstances that represent a fundamental shift in presentation, quality, art/character direction, or what have you would constitute as a significant moment of change.
Beginning of the 3rd Doctor's run, as the show changed it's focus to modern Earth and lost the time/space travel aspect for 3 seasons, along with making the Doctor much more of an action hero and the show filming in color for the first time.
Beginning of the 4th Doctor's run, as the show took on a more gothic horror-esque tone and arguably hit it's high point.
6th Doctor's run, which was the series's low point.
Beginning of the 7th Doctor's run, which lightened the tone considerably after the darker stories of the 6th.
The end of the classic series, the Fox TV movie and the beginning of the revival, of course.
There are probably a lot more that I am missing, but I think I got most of the big ones there.
The beginning of the 11th Doctor's run, due to showrunner Russel T. Davies leaving the show and Steven Moffat taking his place.
I'm probably missing a lot, but I think those are most of the big ones.