Capaldi is my favorite, with Series 9 being my favorite. Series 10 had a lot to love, but I think it fell slightly short due to being a companion introduction AND farewell season, plus having that half-baked monk arc in the middle. Series 8 was good but had a few stinkers - Kill The Moon and the forest one are some of the worst episodes they've done in NuWho.
"It was all a dream!"
Kill the Moon to me was a great episode, but I understand it might be hard to appreciate.
First of all, you need to accept the "moon is a egg" premise. To me, Doctor Who is not sci-fi series, more like... magical science with a inherent silliness, so I don't have any problem with such a premise. Capaldi's smile while he says "the moon is an egg", followed by the incredulous silence of everyone, else also sells the concept. But again, I can see it is not a straightforward premise for all the audience.
Then you have the whole abortion metaphor, which was 100% unintended. Yes, we have several female characters talking about killing a young lifeform, but as the episode writer notes, the various "ABORT" signs referred to the abortion of the mission to kill the moon, so in a way they referred to abort the supposed abortion. It doesn't really work as a metaphor. The intended reading of the episode is that trusting a strange, unknown and weird lifeform is better than being wary of their intention and killing it. It's a beautiful message.
Probably if they had a women editor telling the writer to change a handful of lines and supervising the production, we wouldn't have the message so misunderstood.
"Who was that, Doctor?!"
"The Master... once my best friend, now there's nothing he likes more than plunging my life into chaos. One time, he almost convinced me that I was the origin of my entire species! Imagine that!"
Something like that (except penned by someone who can write natural-sounding dialogue). The Timeless Children thing is probably going to be like the "I'm half-human" revelation back then; it will be mentioned occasionally... but most of the time it will be either to mock it or to try to fanwank it away.
My headcanon is that
the Master was the Timeless Children, and Tecteun was just messing with the Doctor in S13. Martin Doctor is a Season 6B Doctor between Troughton and Pertween working for the CIA, who at the end of her contract was granted a new regeneration and had her memory erased.
Was this the intended reading? No, but screw the intended reading -- it's awful, and didn't really make any sense anyway. This saves most of what was shown on-screen, and actually creates an interesting premise (the Doctor has a bit of the Master inside them!).