5. Just Because He CAN Fall In Love Doesn't Mean He DOES Fall In Love
The transition from a mostly aesexual Doctor to a more romantic Doctor isn't like night and day. The Doctor isn't running around getting married, making babies, or anything like that. He's falling in love, but it's not dominating the show. And before people start talking about Rose and River derailing the show: no they didn't. The show has moved on from both Rose and River. Rose and the Doctor's relationship was central to like 3 episodes. River's romantic episodes--where she wasn't along for an adventure, and where it wasn't about her and the Ponds' history--were 1. Just her Wedding. None of the rest were all about the relationship. And the Doctor isn't sleeping with all his companions. Of the last six full-time companions, he's fallen in love with one. Just one. Maybe two, counting Clara. It's a big deal when the Doc falls for a lady, but not so much that it takes over the show for longer than an episode. Then it's back to adventuring.