As someone born in a desirable place with freedom of movement, it's difficult for me to speak to those barriers from an informed perspective.

It's very complicated. To what extent is progress about improving all places, and to what extent is it about enabling people to move to the good ones? If it is all about enabling movement, then having individual nationalities really gets in the way. Also, cultures that cannot co-exist with others in close proximity also get in the way.

There's an interesting kind of phenomenon where the people that seek a place for one reason change it into another. Personally, I am ok with that. It's what I see around me here in the US, and it seems to be a good thing. However, the US is pretty unusual in that respect. We have a short history, a lot of resources, and a powerful Federal government.

Ultimately, what I hope we see, is a world with freedom of movement, but places with all sorts of cultural and economic experimentation, that we are free to move into or out of. I really don't know if Brexit is a move towards or away from that.