Somewhere in the David Tennant era the train came off the tracks. It started to be about romance, too many episodes were on earth, there were too many folks following the Doctor around and related to him, too much self-reference to previous lives and eras, too many people actually saying “Doctor Who?” out loud. Too few good stories. Steven Moffat took control and things really got awful. In the last few years I can only think of a handful of episodes I really enjoyed. I think the Doctor actors have come off pretty well as characters, but especially Matt Smith was fed almost nothing but crap for scripts. He did as well as he could.
If you go back to the first era the series really petered out during the Colin Baker and Sylvester McCoy Doctors. BBC screwed up the franchise then with poor writers and poor choices for Doctors seeing it still as a children’s program with little potential beyond that, and it’s on the verge now. Similar to what NBC did to Star Trek in the ’60s. Capaldi is a good choice for an actor but somebody has to hand him a bloody script.
You cannot save this by bringing back the Daleks to menace the earth once again. How many times have we seen that? Quit bringing back “beloved” characters from previous episodes, eras, without some original and exciting writing to go with it. Piss on the romance. It was always about affection not romance. A certain amount of sexual tension is good until outright romance jumps the shark; a grasping at simpering sentimentality instead of good writing.
I missed Dr. Who when it went off the air in 1989 and I miss it now.