Donald Draper wrote:
A big question I have always had is it really a time travel series? I am a time travel fanatic. But mostly about exploring history. Yet the show seems to be more about fighting aliens. Or am I wrong?
Yes, it is a time travel series.
When it began, 50 years ago, it was intended to teach children about history, and it did so (Marco Polo, the Aztecs, etc), but if they could go to the past, they could also go to the future. And they typically had better ratings when they showed alien monsters in the future, so they do tend to have their share of them ... but they do still have historical shows, including stories about WW2, Agatha Christie, ancient Venice, etc.
You never really know where you'll find yourself when you step through the doors of the Tardis. Hang on and enjoy the ride.