It's been coming for a while now. The season's opening story was somewhat interesting, but that was owing entirely to Missy (the actress would have been made a good Doctor, really). Outside of that, I was underwhelmed.
And I kept on being underwhelmed. Nothing was awful, but the series felt like it had finally, completely run out of ideas. Individual stories felt like more of the same, and there was little indication of the sort of grand, tricky story arcs that have been Steven Moffat's saving grace.
By The Girl Who Died/The Woman Who Lived, I was seriously considering whether Doctor Who was still worth watching. I was a little shocked at myself. During the Russell Davies years, and even during the early Moffat era, there was no show I was more excited to watch each week than Doctor Who. It was my top show. Could I really just ... stop watching?
As I was watching this episode, which felt so similar to so many episodes before (where are the ingenious new ideas like deadly statues that the series once threw at us with suck reckless abandon?), I realized it was time to stop. I was in the middle of the episode, and I didn't care what happened next. Not at all.
It's not the actors. I always liked Clara, and I like the new Doctor as much as I liked the last one (in both cases, not nearly as much as the first two). It's the writing. The writing has gone to s***. There's no other way to put it. The show is devoid of fresh ideas. This episode is simply a matter of raiding old ideas to piece together a new episode.
Doctor Who is not a terrible show. But it is no longer a wonderful show. There are so many better series out there (The Strain, Haven) that I just don't have time for it anymore.
Will I ever watch the show again? I might look in if I hear Missy is back. Or I might not. It might take a change of show runner to get me back. This series is completely out of steam. It makes me sad.
UPDATE: Years after writing this, I decided to watch some well-reviewed episodes from the Capaldi era that took place after this, and discovered that eventually the show got quite good again. So my leaving Doctor Who wasn't permanent.