Don't get me wrong: I like it! I like that this was just another episode, much like it used to be in the classic show. It wasn't some overblown epic throwing the known universe into mortal peril or dredging the darkest corners of the Doctor's soul. It was just another adventure, with the tension ratcheted up a bit by the return of an old adversary and the clash between the Doctor and one of the companions. Except for Tim Shaw choosing to destroy planets, including the Doctor's favorite, the story was kept small and personal, and to me, this was brilliant.
It's also pretty singular that this episode is understandable with only knowledge of the season opener. A viewer who didn't keep up with the series would know who Tim Shaw was and could extrapolate from Grace's death to understand why Graham wanted revenge. Though, I feel sad for such a viewer, as he/she missed a great season.
The story provided enough peril that it really needed the entire TARDIS team - to rescue the ship's crew, figure out what was going on, and face down Tim Shaw - and didn't need to slow down the action when it focused on this character or that. Interestingly, other than the sniper robots, the team was barely in any personal danger. Instead, the pressure came from what they were trying to accomplish: rescue the ship's crew, save the Earth, not crush the planet they were on with five other planets.
The star of the show - and this seems to be a trend here - was Graham. He was strong enough to go toe-to-toe with the Doctor when it was important to him, and strong enough to change his mind and be the better man when confronted with the actual choice. With everything else that was going on, that was the real meat of the episode, and it's wonderful that the season finale focused on this tiny story. I also liked Graham's and Ryan's solution to the problem of what to do with Tim Shaw. Very fitting. (And of course someday, someone's going to let that bastard out and fuel a whole new episode.)
As soon as the Doctor handed out the psychic blockers to protect everyone's minds, I knew that someone was going to lose one and get into a lot of trouble... and the episode turned that around with a surprise: the Doctor and Yaz voluntarily gave theirs up to solve a problem, and then actually got them back!
A lot of the elements of this story reminded me of old episodes without being rehashes. The planets pulled out of their orbits and stored somewhere to fuel another purpose had me picturing the Dalek magnetron and the Lost Moon of Poosh. And then of course the Doctor went ahead and directly mentioned towing the Earth with the TARDIS. And then Ryan and Graham ducking down to let the robots shoot each other reminded me of "The Day of the Doctor", though at least this time, it actually (almost) made sense that the two sides managed to wipe each other out.
At the end of the episode, my husband said, "That made me sad." I was surprised, because he had been excited about the story after the first couple of scenes. I said, "Oh, you didn't like it?" and he said, "It made me sad that this is the end of the season!" And he wandered off, humming and grinning like an idiot. Thanks, Doctor Who! It really feels like you're back again.