I'd like to invite you to watch a video on YouTube about something called Vertical Video Syndrome:
It's a funny video. And Fafa is a cute beaver.
But he's wrong. When they say "you can't really turn a video" because "televisions are horizontal" and "computer screens are horizontal". They forget about smart phone screens. Because they are not horizontal. And holding a smart phone vertically to watch a video, excuse me, but is just as idiotic as holding it that way to shoot one.
I'm on Instagram just like any other person. And one thing I've noticed is that photos taken in portrait orientation look much better. And I enjoy them, and like them more often than vertical shots (which appear just tiny).
I think YouTube should figure out a way and allow vertical video to be displayed in portrait orientation in full-screen. One time there was a glitch on a recent iOS beta and I could somehow reproduce this behavior by accident - it felt right.
Vertical video isn't wrong. We just need more of it.