Open borders is a great idea but is not compatible with democracy. Garett Jones writes well on this topic. Immigrants from parts of the world with bad institutions will likely lower the quality of the institutions in their new countries, but only in democratic nations.

I prefer other forms of governance to democracy, such as Futarchy and certian forms of meritocracy in which standardized testing and sortiton are combined. One thing radical open borders would do is bring in an era of competition in governance, as for the first time there would be significant competition for citizens. Overall it is a good idea, but those who believe in the welfare state have little choice but to shun it.