The Moffat Regeneration
Steven Moffat wrote some of the best New Who, and personal favourites like The Empty child/The Doctor Dances and Blink and yet my enjoyment of the series as a whole has been in a downward spiral since he was put in charge.
The only explanation that makes any sense to me is that around the time Moffat took control of Doctor Who, he regenerated into Jeph Loeb. The hallmarks are all there; the focus on superficial spectacle over solid story, guest stars shoehorned in at every opportunity, regardless of whether it screws with established continuity or is remotely appropriate to the plot. Convoluted stories that don't work if you think about them at all...
The kicker for me was in the latest episode Let's Kill Hitler, which apart from bringing in one of history's biggest guest stars only to lock him in a closet after five minutes and forget about him, contains one of the classic Loebisms from Hush: introducing a major character's life-long best friend who has never previously been mentioned in the story while having them be central to overall continuity.
At first I thought it was some clever time-travel thing and the Doctor would notice that Amy and Rory's past had been changed, or that their memories had been tampered with, but no. Apparently it's merely the same kind of bad writing that gives us time-travelling Autons making a plastic robot copy of Rory  for their Roman army at Stonehenge, even though they'd never met him.
And that's not even addressing the throwaway concept of previously unmentioned time-travellers going around assassinating history's greatest criminals, but who are so crap that instead of surgical strikes to a time and place where the person won't be missed, they are entirely years off the mark, and when they screw up they leave extremely advanced technology lying around in Hitler's own office for him to reverse-engineer into a super weapon. But the Doctor doesn't seem bothered about this kind of tampering with time, so let us not mention it again.
1) Though he managed to destroy any interest I had in the scary stone angels by bringing them back and overexposing them.
2) Daleks teaming up with Cybermen? Did Moffat miss Doomsday, where the Cybermen outnumbered the Daleks thirteen million to four and when they propose an alliance the Daleks sneer at them and kick their shiny metal asses?
3) And even underlining how poorly this is being shoehorned into the plot by handwaving why she didn't appear at both her best friends' wedding, but not why nobody noticed at the time.
4) Who was dead at the time.
5) Did the plot of The Pandorica Opens/The Big Bang make sense on any level at all? I'm sure there are devoted websites out there taking it apart and bodging it back together with ingenuity and convoluted assumption to somehow force it to make sense, but personally I think that's the job of the guy who was paid to write it. And possibly the script editor, who was also paid to check it made sense.
6) It's not like there's ever been previous stories about the Doctor dealing with a Time Meddler...