Actually, I thought it began much like some kind of rejected script from
Black Mirror, with the usual Dr. Who silliness obviously, like walking into lamp posts.
I can accept they would have difficulty with directions, but they walked perfectly okay within their bubble.
Anyway, I didn't really think much of it at all until it took the dark and unexpected turn later, and I like that change in step, even if it did leave a lot of questions without answers.
how casually she sacrificed Ricky
It was either her or him, but she'd made out how wonderful Ricky was, and I think, of all the inhabitants of that world, he was most capable of survival outside of it. He certainly wouldn't have turned down the Doctor's offer. She proved herself to be shallow and dim-witted.
surely the AI devices did also and so knew his real name?
They ought to have, and she was too stupid to have discovered anything they hadn't already fed to her. I wondered at first why they had chosen to contact her when some of her 'friends' seemed more open to alternative ideas, but the explanation for that came with the alphabetically ordered list.
I didn't like the ending and the implied reason why they wouldn't accept the Doctor's offer.
a more subtle take on racism
At first I thought the "Racism is Stupid" message only worked because of the colour of the Doctor's skin (and that every inhabitant was white, rich, 18-30-year-olds.) Except that on reflection, two things show this was the message: Lindy being surprised that the Doctor and Ruby could be in the same room together, and Lindy saying that she thought the Doctor that she blocked, just looked "the same" as the Doctor who had hacked the block.
However, it could easily have worked as other analogies (without getting too political) where people facing some obvious choices prefer to believe in lies because they want to believe in an ideology whether that fits with the facts or not. It could also have been symbolic of how some people react to scientists who are alarmed and warn about Climate Change. Anyway, whatever it was it is a case of Darwinism in action!
no real explanation of what had happened on the Homeworld.
The AIs destroyed the Homeworld first. The Doctor and Ruby had already spoken about "Mummy" and Ricky confirmed she was dead, so her appearance in the Bubble was a Deep Fake created by the AIs.