I just think that Doctor Who lost all the Tumblr fangirls once Matt Smith left because it was the first time the main lead wasn't a pretty young man since Eccleston.
One of the worst things that ever happened to Doctor Who is that they needed to pander to fandom shipping.
I was never a fan of Old Who, but New Who was always so cringe to me when the subject turned to whatever pretty young girl was swooning over the Doctor, because first of all, I think the trope of extraordinarily old being falling for dewy ingenue is fundamentally gross. We could turn that discussion to the acceptance of grooming, but I don't really want to go there right now. Second, though, is that it assumes that someone that old
can even fucking relate to someone that much younger.
There was one scene in Capaldi's run where he called a couple of people "screaming kids" because they were threatening each other with war, and finally and for once, somebody wrote the Doctor as someone who is his age: someone with a perspective of centuries, who's seen the fallout from war and how unpredictable and ugly it is.
That's who the Doctor should be. Him and plenty of other modern writers of characters in TV shows that seem to think all of these older characters aren't complete without a love interest, or can't conceive someone their own age exists, but is an appropriate companion. Even River Song, though contrived to be old, still felt kind of icky because the Doctor knew her as a baby.