[user104658]

Originally Posted by Mystic Mock

You have a point on the race change.

But tbf changing a character's sexuality is really bad writing under most circumstances, and the few reasons that a Show can come up with that is good writing, Doctor Who fails to meet the criteria.

- He isn't a teenager who's about to become an adult, where you could argue that he is still learning about himself.

- And it's not a Remake/Reboot series with an alternate timeline, where almost anything can change from the original version.

It's well established though that the regenerations are not just a "face change", it's still essentially the same person with the same memories but the entire personality can change; one of the clearest examples of that was Matt Smith > Peter Capaldi and they covered it quite well in the episode... having the dying Smith-doctor call Clara from the past to explain to her that she might have to really "look deep" to see that it's still him, because he might seem very different. But they all change their style, quirks, personal likes and dislikes, mannerisms etc... no reason different regenerations wouldn't find themselves attracted to different people.

Besides; Eccleston and Smith's doctors were blatantly bisexual-ish / "down for whatever" and Capaldi was for all intents and purposes entirely asexual. Tennant had an eye for the ladies definitely but other than that, doctor's an alien... I don't think he could ever have been classed as "straight".