So, I've now caught up through the Zygons episodes, and I think I'm starting to pin down what I think is wrong with this season.
1. The first episodes in these two parters are usually kind of "meh." Like, at best, they're mildly entertaining, and at worst, they're boring and I find myself mentally checking out entirely. I still watch them because I want to know what's happening at the start of the next episode, but they often don't seem to add very much to the story. In essence, the stories seem like 55-65 min of actual story that you need, but with an additional 30 minutes of blah thrown in. I tend to enjoy the 2nd episodes of these two episode arcs a lot more. But I find myself just blandly ignoring what are supposed to be laugh lines because I'm just not really engaged by the show.
2. Clara is a hindrance to making the Doctor interesting. So far, the best episode of the entire season is the one where she hardly appears at all: The Woman who Lived. That episode was way, way more interesting because of the concepts it dealt with, and how well Maisie Williams played her part. And then Clara shows up in the Zygons episodes and I just find myself bored to tears. And yet, when the Doctor is off palling around with Osgood, things were interesting again (mostly). So, yeah, Clara's a problem now.
3. The problem with Clara isn't just that she pulls focus from the Doctor, but rather that she pulls focus and nothing much comes of it. I know a lot of people really disliked last season, and disliked Clara in it. I was happy to tolerate it, though, and even enjoyed it for two reasons: (1) it was supposed to be her last season, and (2) she really did seem to develop as a character. The season had a clear arc for her journey, and it ended when she walked away from the TARDIS entirely. Now that she's back, though, her character seems totally aimless, and I think a lot of it is because the writers have no clear plan for what to do with her. There's no thru-line to her story, so she either has no character at all and is just kind of...there...doing stuff...or she's inconsistently portrayed with what's come before. The greatest sin, I think, is that the writers have done nothing to show any real impact on her as far as the events of last season. She's just...fine. It's like Danny never existed, she feels no pain from his loss, she has no sense of consequences for her choice to travel with the Doctor. In essence, Clara feels less fully fleshed out this season and more like she's back to being "The Impossible Girl" or just some pawn that the writers can move into position to accomplish a task. I think she really, really needs to go. Don't get me wrong. Jenna Coleman is a terrific actress, but they have zero idea what to do with her now and it's hurting the stories as a whole.
4. This is a subtle point, but the way the Doctor is being portrayed this season is also kind of haphazard and often underwhelming. The whole "shabby granddad" look really does not work this year. I get that Capaldi wanted to do a costume that anyone could do, but it's making the Doctor less distinct. And, unfortunately, the writers aren't giving him enough material like he had at the end of the Zygons arc (which was AMAZING) to offset that. Also, his guitar playing. I get it. The Doctor plays guitar. Also, as someone who can play guitar, I really DON'T appreciate when the producers dub in a piece that is clearly different from what he is playing. Seriously, the Zygons episode opened, I think, with him playing the Star Spangled Banner a la Hendrix...but if you watch his fingers, it's wrong. First, the notes would have been way higher than what we heard. Second, they were playing sustained notes while his fingers are moving on the damn fretboard. I'd love to hear what he originally played, but I guess that's a bit much to ask. Also, I'd like to see him play less. It's becoming a pointless gimmick now. It was cool initially, but it's being overdone. And lose the ****ing sonic specs. They suck. All of this, I think, is making the Doctor less distinctive as a character.
Beyond those issues...I'm just finding it really hard to get excited about the show anymore. I don't look forward to it. I watch it in the hopes that it'll get better, but at best I get a "eh, that wasn't so bad" episode, usually at the 2nd part. I want to keep watching the show, but I want it to do better. Much better, actually. I think, however, that Moffat really needs to go for that to happen.