Don't tell me you buy into this Moffat's Who was hugely sexist (and RTD's was not at all) and ignore Moffat himself has hinted at a woman Doctor? (I have my own kind of mixed views on that but that is a whole other debate).
What's wrong with just creating new, awesome FEMALE characters rather than just converting old ones that were male? Isn't this just another variation on the sad lack of imagination of the entertainment industry nowadays with going with "reboots" - and yes I know there are some good counter-examples - BSG (with a female Starbuck!) being one of the best - I'm just wishing for originality!
Moffat has straight up said "don't hold your breath for a female Doctor".
Personally tho, I think River deserves her own show.
There are new and original female characters, but Marvel has recently started realizing that there's a need for Legacy characters. Granted, Cap's been what 7-8 people, there's been at least 4 wielders of Mjølnir (one of which was Jane Foster). Having Sam being the new Cap, the new Thor, Kamala Khan as the new Ms Marvel, Carol being Captain Marvel, Annabelle Riggs being the new host for Valkyrie (think Donald Blake). It's all about creating legacies, similar to the Batfamily, The Flash, etc.
No one says "Oh where's the originality" when Dan Ketch became the new Ghost Rider, or when Sam Alexander replaced Rick Rider as Nova. It's only when Miles Morales became the new Ultimate Spider-man, Renee Montoya became the Question, etc. The whole "should be an original character!!" pops up when traditionally white male heroes are replaced by a minority/LGBTQIA/woman.
In the last couple years (and including the Cap/Thor thing) we've also gotten; Kamala Khan (Ms Marvel)
Cindy Moon (Silk)
Angela (tho, technically, that's Gaiman just bringing his character from Image to Marvel)
Adam Brashear (Blue Marvel)
Aya Ayala (technically she's a legacy too, White Tiger)
Victor Hernan Alvarez (Power Man, legacy)
Benjamin Deeds (Morph)
Andrea Brenton (Mania, another of Venom's spawn)
All these characters are minorities, LGBTQIA, women (or in cases combinations of 2 or more).
And while Marvel's getting better at representation, they turn around and do problematic **** like making Mystique straight (and Nightcrawler's origin) after decades of Raven's relationship history with Irene Adler (Destiny).