When countries grow together, different nationalities come closer, cultures respect each other and can live together, this is desirable and worthy of support.
Creating a bureaucratic, Babylonian-chaotic translation complex with free borders and a free economy does not constitute growing together. The current EU is suffering from the hope that jointly binding rules with a common currency would lead to greater understanding and unity in the long term.
What the British have anticipated with their Brexit threatens the entire EU in the medium term. Disintegration, members leaving due to lack of interest, economic upheaval and permanent crisis.
This does not necessarily have to be the case, but it will inevitably happen if the EU in its current form is not radically changed towards a common European understanding and away from the interests of individual states, tied into ever more restrictive bureaucratic rules.
A united Europe must be shaped by the citizens of all participating countries and not by political elites who send their desired representatives and who have never been confirmed by the electorate. Europe’s democratic legitimacy suffers just as much as the individual local democratic systems do.
A democracy is an evolving construct, not a rigid structure which, once designed, never needs to be improved. This is the main problem of modern democracies. A fundamental improvement of the inherent rules (e.g. the Basic Law) is hardly possible, but is absolutely necessary in a rapidly changing world.