Just watched it and... hmmmmm....
I have no real issue with fiddling with canon, but this just all felt a bit contrived, and rather more than that, illogical.
Why would the Master be quite so enraged...? I get that he's a mad villain (and by "mad" I mean, way overacted. Missy was rather better), but the way it was shown didn't really make much sense.
It would have been far more interesting having it be the Master who was the Timeless child, thus better explaining his rage at being experimented on for eons, and adding a layer of guilt to the Doctor for being part of the race that was responsible, as well as knowing that she was part Master.
Right up until the reveal Me and Mrs Ident were speculating the same thing. It just seems a bit vague that The Master would commit an act of whole species genocide based on the assumption that he was a bit pissed off over The Doctor having shaped his people and society. The motivation isn't quite right. It's iffy.
Personally, I think that The Master as the Timeless Child would have been the stronger play for the story, with the Doctor realising that the only way she could stop him was to literally snub out every last trace of her own people.
But I'm also aware that this was not just about a single story. It was about embracing some of the abandoned masterplan for the series which was jettisoned back with the cancellation of the show at the end of the 80s. A plan which was intended to restore some greater sense of mystery to The Doctor as a character.
It's been done in a bit of chaotic and messy way, with plotholes aplenty to explain away, but from an ongoing story POV one of The Doctor's greatest strengths is that regardless of where they are, and when, they have an implacable sense of self. Their past, their character, their moral fibre. The belief that they are a force for good in the universe. And that any race which feels otherwise does so purely because The Doctor stopped them doing something that they wanted, which would have had horrible consequences.
The hidden memories of The Division somewhat changes that. It seeds doubt in The Doctor. The realisation that there are potentially many lives which The Doctor not only doesn't remember but in which they may not have behaved quite so altruistically. Certainly badly enough to be labeled a fugitive. That genuinely they might have interfered unjustly in the lives of others. Something which has the potential to seriously mess with The Doctor's sense of values.
That's a very interesting notion. I just don't feel that it's been delivered as well as perhaps it could have been.
The more I think about it, the more illogical and irritating it becomes*.
In trying to tie up loose ends, they've just created another issue; two hearts.
If the Doctor is a different species, then why do they have the same two hearts as the Gallifreyans...?
Basically, Chibnall has just created nothing more than a somewhat dark superhero origin story.
An orphan, with powers beyond the like of which their adopted world has never seen...? SuperWho, anyone...?
It's annoying, because up until the final episode, I'd rather enjoyed this series (season if you talk American).
*I'm aware I'm getting annoyed by a kids TV show, and probably just need a morning coffee.
They showed the scientist woman listening to the timeless child's heart with a stethoscope. My guess is they had one heart, untill they spliced themselves with timeless child DNA.
That's the most viable option for an explanation that I can think of. As to whether that will ever be made plain to viewers, I guess we'll wait and see. But it's not the only loose end created here.
For one, from the recent-ish past, there's the issue of Clara. Clara supposedly saw and interacted with the entirety of the Doctor's timeline. How come she never saw the parts with The Division?
Where does the Fugitive version of The Doctor fit in chronologically? Because you would assume from the way it has been shown to us so far that The Division happened pre-first Doctor. But the Fugitive Doctor's buried Tardis is a police box. Presumably because of the legendary 'stuck chameleon circuit'. Which happened after the Hartnell era Doctor stole it from Gallifrey. So where does this fit?
Then there's The Master's past incarnation as Missy. She talked about her and the Doctor running around as Children. That now seems pretty unlikely. The timelines don't quite tally.
So, yes. Contradictions aplenty. I do think that going forward this could introduce some very interesting possibilities. But it's all a bit messy, nonetheless.