I'll start off by saying: Don't be fooled by the picture. Yes, I've been in the Tardis, but I am no Dr. Who expert. My take on this could be completely lacking in the needed context and I may be completely off base here.
I've seen all of the most recent incarnation episodes (Doctors 9, 10 and 11), but only a few of those preceding them. Yes, I know the quality of both writing and production has been mixed, and yes I've seen the Douglas Adams episodes (what do I look like?) Here's what I've gleaned from my limited viewing: The whole "thing" about the doctor can be summed up in this exchange, from one of the earliest episodes ("The Expedition"):
Ian: "They (the alien people they have befriended and who are threatened by the Daleks) have one great disadvantage: They have no arms or ammunition!"
The Doctor: "Well that's alright young man, the mind will always triumph!"
For me, Doctor Who is all about the mind triumphing over brute force. It's not always explicit, and the good guys don't completely disavow violence. But at its best, this is the theme that drives the show. And at its best, the Doctor and his companion/s are thrown into impossible situations out of which they must extricate themselves using their brains (and sometimes dumb luck.) This is what makes for some of the best drama.
What makes it even more compelling though, and especially with Doctor #10 (David Tennant), is what emerges as the core of the Doctor's character: His passionate love for humanity and his rejection of violence.
When Doctor 10 regenerated, Doctor 11 (Matt Smith) took some getting used to. But once he found his feet, my husband and I came to like his geeky goofiness. He was never Doctor 10 though, and now I think I know why.
Recently, my friend Darwyyn Deyo sent me this article, "How Moffat Ruined Doctor Who for My Little Sister." I admit the sexism hadn't caught my attention (although had I watched it as an eleven-year old girl, I'm sure it would have. One is more attuned to such things at that age), but I found myself nodding along to the comments about plot inconsistencies, why River had to stay locked up, the credulity-straining breakup and getting back together of Amy and Rory, and Moffat's apparent need to "make everything Epic all the time, there’s an explosion an episode."
For me, the Moffat episodes, while full of explosions and lots of plot details, are lacking in what makes The Doctor The Doctor. I love some of Moffat's work: "Blink" is one of the best Dr. Who episodes ever - although not for the reasons that make The Doctor great. And I am a fan of "Sherlock". But I think Moffat brings too much of Sherlock to Dr. Who. And the two characters could not be more different.
It hit me in a recent episode, where the uninteresting (as compared to previous companions) Clara confronts The Doctor regarding his relationship to humanity, asking "what are we to you?", wondering if all of our accomplishments, our lives, mean nothing to him. I knew immediately what the 10th Doctor's response would have been: "You are everything." The 11th Doctor's response was that of a bad boyfriend. A very bad boyfriend. The kind who reads too much Sartre and is very impressed with his own cleverness. His response was that of the Cecil Vyse of time-travel:
"You are the only mystery worth solving."
I may not be an expert in the domain of Dr. Who, but I know this is not how The Doctor would respond. This is how Sherlock would respond. And Doctor Who is not Sherlock. He is brilliant, yes, but that is not what makes him special. His relationship to humanity is not one of an investigator or a scientist trying to "figure out" the mystery of humanity. He is an advocate of humanity. His aim is to protect and care for humanity - and he is effusive in his appreciation of it along the way, whether or not he fully "understands" us.
So here's what I think: I think Moffat is better suited to the Sherlock series. I think he doesn't get what makes The Doctor great. It is not the same thing that makes Sherlock Holmes great. A mystery - no matter how interesting - is not enough to make a compelling character. The mystery of who Clara is and why she seems to keep coming back from the dead may seem fascinating on the surface - but it is not enough to make her as interesting to us as the shop assistant Rose Tyler, or the temp from Chiswick, Donna Noble. Nor are explosions and "epic" situations enough to make a show great or a hero compelling. For now, we're still watching the show. We like Matt Smith, we're invested in the 'verse, and it's not awful. But I can't help feeling that it is no longer Doctor Who.
UPDATE: It has been mentioned to me that Dr. Who has been "ruined" before, and has managed to bounce back with stunning success. I believe this, and I believe that the series - and the underlying idea - is strong enough to do it again. So I'm not too worried. I'm just not crazy about the direction it's taking right now.