I see what it's trying to do, too. What it does isn't done badly; it fits the dark fairy tale ethos of the Moffat era. But it can't be taken in a vacuum. Taken on its own, in a vacuum, it might even be effectively done. But it can't be taken in a vacuum. It has wider implications for, really, the entire history of the program. It answers questions (or at least starts answering them) that should never have been answered, and it opens the door to more exploration of those questions. The Doctor's history turns on itself like the Worm Ouroborous.