At a time when kids are very likely to know a teacher--or relative--who has been to war, Doctor Who spends a series dealing with it.
Doctor Who has a lot in common with Harry Potter. First and foremost, they are stories aimed at kids. The Doctor was created back in 1963 to be "H.G. Wells meets Father Christmas," and has stayed fairly true to that formula ever since. Because of this, expecting Doctor Who to be Battlestar Galactica is a bit like expecting Harry Potter to be Game of Thrones. It is meant to be whimsical, to have its absurd moments of wild imagination, and to the adults in the room, to frequently be unbelievable. When I hear someone complain about Who's sillier moments, I wonder if they are the kind of people who also complain about the violations of basic physics in the old Warner Brothers Roadrunner and Coyote cartoons.