>changing citizenships should be as easy as changing jobs

Even removing legal barriers, it can't be as easy, since changing citizenships necessitates a very large geographical move, while changing jobs may a require a large move, a small move, or no move. Changing countries changes your entire life - you are leaving your home, its culture, and everybody you know there. It's cruel to imply the people who would be made miserable by such changes simply don't matter.