The guy who can literally white eyeball himself into anyone and anything and chose NOT to commandeer a dragon at any point?
The guy who chose NOT to stop Daenerys from melting the population of an entire city?
Couple of objections here.
One, dragons in GOT are smart. Like, really fucking smart. Like, maybe as-smart-or-smarter-than humans smart. Drogon melted the Iron Throne because he seemingly understood that it was his mother’s lust for power that got her killed.
So if the dragons are that smart, then there’s no real benefit to Bran seizing control of one, unless it’s to seize control of Drogon right there at the end and fly Dany into the ocean. But even this may not be possible, because…
Two, we have no reason to think that Bran can seize control of a developed, intelligent mind. The only person he’s ever mind-controlled is Hodor, and Hodor is, well, frankly quite dim-witted. Bran even had trouble holding onto Hodor’s mind at first — I seem to recall Hodor kept bucking him off. Maybe that only happened in the books. I can’t remember.
Either way, the suggestion that Bran could mind-control a person of average intelligence is unproved, and the suggestion that he could mind-control someone with an iron will like Daenerys is dubious at best.
Which brings me back to my first point: if Bran’s ability to mind-control is limited by the intelligence of the subject, and if dragons are really fucking smart, that might also mean it’s impossible for him to control dragons.
— — —
But there’s another reason why I’m not so much bothered by Bran taking the throne.
It didn’t get addressed much in the final episode, but we’ve been told earlier in the series that Bran is a husk of who he once was. His new perspective granted to him as the three-eyed raven has made him dispassionate and, well, kind of checked-out.
Which to me suggests that he’s just a figurehead, and that the real person who wields power now is the Hand of the King. Tyrion. And I like that idea very much.