I wish DW fans would just stop talking about already replacing the 12th Doctor or begging to bring back Matt Smith- seriously, it's super rude. Capaldi is a great actor and a great Doctor, and if you don't like him, then just deal with it. I happen to know plenty of people (like myself) that had to clench their teeth and deal with Matt Smith for 3 seasons even though they couldn't stand him.
Also, Capaldi is a super Whovian, he's always wanted to be the Doctor since he was a kid- now he's living the dream. How would you feel if you got to fulfill your childhood dream only to find out people were ragging on you because you weren't 'young and handsome' and they wanted to replace you. The Doctor is badass at any age and you're not a true Whovian if you can't love the Doctor just because he looks older now.
If you've got a problem, blame the shitty writers. But seriously, stop already planning Capaldi's going away party and talking about who should be next as Doctor.
One more thing, A female doctor is a great idea in theory, but a terrible idea in reality. If the writers are blowing it big time with an actor as good as Capaldi, they'll make Doctor Who into a total dumpster fire if they cast a female as the Doctor.
Now everyone just shut the fuck up and enjoy the show