When talking about the EU barriers in particular, I'm too young to remember anything else. The only big change I remember was the Euro being introduced, which only made buying stuff a bit easier on holidays. But I do know a bunch of people that have benefitted greatly from those removed barriers. Especially at a university you meet so many people from other EU countries or people who have lived abroad for a while that Europe might as well be a federation.

Personally, I think having great mobility will inevitably lead to great places. How great that place is depends on where its drawing it's people from. I grew up in the capital of a rural-ish provence, where not infrequently the local newspapers lamented that capital for draining the countryside of people and knowledge. But at the same time, there are articles out there talking about the mobility of people from those peripheral provinces of the Netherlands towards the big cities like Amsterdam and Rotterdam, which is a move I did myself last year. And there are people leaving those places to move to Berlin or London. Each successive place can be seen as contributing more to progress. There's a reason the very first thing urban geographers are taught is Christaller's Central Place Theory - while it is outdated, the idea of a hierarchy of cities is still relevant.

The degree to which culture plays a role in this can definitely be argued over, but as someone living in a culturally rich and very dense country I feel like there is always room for cultural diversification and experimentation.