If I imagine a completely open world with no visas I think the "first world" would stop being desirable. USA and Europe would be flooded with hundreds of millio

If I imagine a completely open world with no visas I think the "first world" would stop being desirable. USA and Europe would be flooded with hundreds of millions of people and would develop giant slums. It would be bad not only for the current people that live there but also for the people that currently want to move to a better place since there wouldn't be a better place to move to.