I agree, and those "moments" that Moffat writes are absolutely brilliant. A scene as simple as the Doctor going to Amy and Rory's house for Christmas dinner made me want to start balling. The scene in "A Good Man Goes to War" where the Doctor confronts Colonel Runaway and warns him never to get to him through the people he loves sends chills down my spine. So many little, emotional moments are the main reason I keep watching, and I can let some of the plot holes and inconsistencies slide...but Moffat, if he is in fact as good a writer as he shown he can be, should be able to limit those inconsistencies a lot more than he has.
I've had similar thoughts. I watched "The Wedding of River Song," an episode that was twice as long as its story demanded (the whole first half is a pointless runaround), and I wondered what happened to the writer of "Blink." They are the same person, aren't they? What struck me is that the person who wrote them
is different, though -- one's responsible for an entire series, the other's just a freelancer working on someone else's series. There are different demands on the two men, in terms of time, creativity, and responsibility. And I think the Moffat of "River Song" has spread himself too thin.
It's not that being
Doctor Who's showrunner is outside of Moffat's skillset -- he's been the writer/producer of other successful series in the past, after all. It's that Moffat isn't good at the big stories. One story, a script or two, fits his artistic sensibilities in a way that a whole season does not. (It also probably fits his time better; I suspect that Moffat isn't capable of achieving the RTD feat of producing multiple consecutive series.) And I think he got lucky with season five. First, there was a gap year going into it, so he had a full year to get his ducks in a row. And second, he had a big story to tell and he pulled out all the stops for it. That's why season six feels so
off compared to season five; he didn't have the same amount of time to consider it (plus, he had a new series,
Sherlock, to worry about), he didn't have any new ideas (hence, his return to old successes, like River Song and timey-wimeyness), and thus he flailed in the same way that writers do with second novels and bands do with second albums, because they've used up all their good material. Season six exposed Moffat's limitations as a showrunner, and they don't bode well for changed circumstances for season seven and the anniversary.
What's unfortunate about this is that Matt Smith is quite enjoyable as the Doctor, and though it would be interesting to see what he could do with different material, based on the mutual praise society between Moffat and Smith it's likely that they will leave
Doctor Who simultaneously.