Does anyone wish to disagree with when I say that Capaldi was the “depressed doctor”?
I would say he is the latest in a short line of Curmudgeon Doctors. The First, The Sixth and The Twelfth could be distant, short tempered and have very alien values. But seeing 12 on top of a tank, playing the theme tune on an electric guitar wearing shades it’s hard to see him as ‘depressed’. There are lots of different modes of depression.
Moffat has with his version of Sherlock depicted some of his ideas of what people on the spectrum are like. The Doctor being an alien has sometimes an alien outlook. He isn’t necessarily mean he just doesn’t understand things in the same way we do. As Colin Baker once put it “stepping over a field of corpses to weep at the death of a butterfly”.
I think after the War the Doctor became increasing the focal point of the universe (or even the multiverse by the end of the 10th Doctor’s tenure). I think this manifested as a crisis of identity in the 12th. “Am I a good man?” can you wear that badge when the most blood drenched monsters of creation run away at your command? And then you have Missy. Basically him but lacking a few vital mental components like empathy. But sometimes the Doctor also lacks empathy (why he needs the very funny crises cue cards) so how are they different? This self reflection I think sums up the Twelfth the most.
He delivers a lot of soliloquy, Heaven Sent (arguably the best episode ever made) is almost all soliloquy and self reflection.
Interestingly at the beginning of the 50th Anniversary episode Clara is writing a quote from Marcus Aurelius (and this is the first time we see the attack eyebrows). “Waste no more time arguing about what a good man should be. Be one.” The Twelth Doctor spends most of his first year fathoming if he is a good man and what that means. Towards the end, facing highly probable death he delivers the final of many impassioned monologues (this time to the Master, his dark reflection) Spoilers for those who haven’t seen it yet, https://www.youtube.com/watch?v=GOaVJufPqUU
He acknowledges that the Master has changed for the better, albeit only somewhat and with her own motivation for doing so. This fuels his own weariness of continuing to change. If you keep changing the parts of the mop you still have a mop but if you change the head to a broom is it even remotely the same thing? Maybe the Doctor would be worse than the Master was (as seen with the Valeyard).