Honestly I think the most jarring part of the Doctor Who change is that the JW Doc is much more similar to the Tennant and Smith doctors, and not at all like the Capaldi doctor, but there are valid in-universe explanations for why that would be, as there have been for all of the regens since the reboot.
Eccleston turns into Tennant because he has a cheeky boner for Rose so he becomes a younger, more modern, more fashionable doctor. It all kind of goes to **** for Tennant so he becomes a wackier, more childish, irreverent doctor in Smith who goes through several war-like, universe-ending scenarios, gets gradually angrier and more jaded and literally much "older" which ends up being reflected in his transition to Capaldi, who starts off angry, lonely, uncaring and quite selfish but "heals and learns" over time before regenerating into the much lighter and more "Tennant and Smith like" Whittaker who has a focus on being surrounded by people and family. Unfortunately, the Brady bunch companions don't necessarily WORK very well, and it's a huge part of the clunky writing, but still - all of the lore works fine.
Sorry, I'm aware this is a Bond thread.
