So the Master returns.... the Mistress... Missy.... returns as a Time Lady and .... converts all the dead in graveyards into Cybermen under her control and.... uh...
I've just watched the concluding episode of Season Eight of Doctor Who and I have no idea of what I've watched. I do think that Michelle Gomez makes a magnificently mad version of the Master. I think the image of the Cybermen flying past a Travelodge and rising from the graves of Earth is amazing. The dialogue is beautifully written and emotions run rampant. The actors are so good that they can make any line that Steven Moffat writes sound good.
However, the story logic of this episode and issues of continuity make me think that Doctor Who has Jumped The Shark. Mr. Moffat has written himself into corners and gotten out of it by distracting his audience with high-speed film-flam before, particularly with Season Six's "The Wedding of River Song". All too often, people confuse the boundaries of science fantasy and assume you can do anything. However, there needs to be an internal logic, and the sudden upgrade of Cybermen at the hands of Missy's Time Lord technology completely rips apart the logic of how Cybermen have been established as behaving. It's too abrupt a change and reduces story logic to mush. If anything is possible, then nothing is really surprising, even if you shout "Boo!" and whip it past the viewer very fast.
Judging by the comments already up, this seems likely to be an unpopular opinion. Well, it won't be the first time.