In terms of evolution, the problem with foot voting is that it isn't a very precise selective pressure. When you leave government A (GovA) for government B (GovB)... GovA doesn't know why you exited and GovB doesn't know why you entered. In economic terms... the bundles are huge. In programming terms... the mechanism is monolithic.
If neither GovA nor GovB knows whether you foot voted because you wanted to get away from your crazy ex or because you preferred GovB's public school system... then the rate of evolution is going to be super slow. The selective pressure is way too vague.
Foot voting should always be an option, but if the goal is to improve governments sooner rather than later, then you need a mechanism which doesn't force you to throw the baby (good traits) out with the bath water (bad traits). In economic terms... you need to unbundle government. In programming terms... government has to be more modular.
"economy" already mentioned Tiebout model... Exit, Voice, and Loyalty is also relevant.
GovA doesn't know why you exited and GovB doesn't know why you entered.
This is true for individual migrants. In case of large migration waves (e.g., East Germany to West Germany), the reasons are usually obvious.
Historically, the evolution of government systems was mainly driven by violence, with invasions and revolutions being the principal agents of selection process. The rules of the game were predetermined by our environment - land was a limited resource, for which our ancestors had to compete, if only to ensure the survival of their descendants.
The 20th century introduced a game changer. As agricultural productivity in developed countries rose by orders of magnitude and natural population growth practically came to a halt, possessing a large territory stopped being a necessity. Countries with little arable land, ultra-high population density and no natural resources can now not only feed their population, but also achieve top living standards. These changes may open a fundamentally different route for societal evolution – one that would not be based on violence or compulsion.
A small thought experiment - imagine what would happen if central governments cede most powers to smaller territorial units:
Unfortunately, there are serious obstacles to the successful implementation of this idea:
Do you think these problems are solvable?