The series has not aired yet and new series trolls are giving this series 5 stars along with classic series fan bashing with offensive remarks such as manbabies and knobs. I will reserve how good it is until i have watched the episodes.
Timelords cannot change sex cause Time ladies and Time lords regenerate differently. When the doctor has regenerated it has been a random pot luck process but when Time Ladies have regenerated they can choose what body they want such as Romana copies the body of the princess Astra and River Song picks a dress size. In Mark of the Rani the Rani makes a comment to the sixth doctor that he is stuck with what hes got, she can choose her appearance.
Having rewritten the rules of regeneration and crapped all over the shows history just to tick all the PC boxes lets hope we get a good series.