-To start with, the season should have more episodes. Many series are having this problem of not being able to develop enough with the few episodes that Disney releases. (Just look at the Marvel and Star Wars series, most of the ones considered the best have at least more than 6 episodes.)
-Second. Belinda's development was terrible. What we know about her can be summed up in one sentence:
She's a nurse and she really wants to go home.
-Third. This whole story about the world of desire between the Doctor, Belinda and Poppy was so uncomfortable (for me). I don't even know how to describe how wrong it feels.
Up until the part where it was all fake and it seemed like everything would go back to normal once the Doctor saved the day, everything was fine. Then they decided that the child was really their daughter.
-Once again, going back to Belinda's development (or lack of it), it seems extremely uncomfortable and confusing for her, but in the end she doesn't choose anything and is forced to think that it has always been this way.
(The good thing is that, from her point of view, she doesn't remember the truth and for her everything is fine. But from our point of view, it's so… questionable…)
-I think the issue of Time Lords being sterile was a cannonball in the script of the entire series.
The first episode of all literally introduces Susan Foreman, the doctor's GRANDDAUGHTER, and he has said several times that he had children in the plural.
Could he have adopted? He could, but I personally believe that if he had the habit of adopting, they would have to come up with a very good excuse for him to have stopped doing it, since we have already seen them with children, and we know that they would give a better life to all of them if they could.
-The Rani was a waste, she had so much potential. If they hadn't decided to bring in Omega (another waste) she could have been an incredible villain.
I mean, she's a Time Lord scientist with no attachment to life. That's a LOT of wasted potential.
-Omega should have been impactful, the true villain powerful above all others, just like the Doctor's entire species has always been treated (so the first of the species should have been even worse). But he wasn't.
It was so meh that I don't even have anything else to comment on.
-There was a lot of expository dialogue throughout the season.
Who is Rani, what she does, what she did, who she knows, her goals, who is Omega, why Poppy is important, among other things, there is literally an entire section where the characters explain to each other and consequently to us.
Nothing is shown, everything is explained and chewed over for you who don't know Classic Who.
I think it's okay to bring things from the classic era, but they should introduce it as if we had never seen it before instead of telling us.
I know a lot of people don't like Timeless Child, but it would have been better if they had continued developing it to maybe improve it instead of ignoring it to create something worse. (Not a worse idea, but the story overall is worse, even disrespectful. I'd rather rewatch the Timeless Child arc and the master dancing Rasputin endlessly)
There are probably more, but the post is already very long and my brain is already burning from analyzing and translating my conclusions into English, which is not my first language.
anyway it's just my opinion and I would love to hear yours to complement or change my analysis