Of course I also understand that unrestrained migration right now would cause massive problems. The real problem here is not the migration itself, but what's causing it. Most people (apart from some adventurous souls) don't normally want to leave the place they were born and where their family lives, except when driven to leave by circumstances, whether those circumstances are poverty, civil war or climate change.
If we have a problem with migration, we should do more to address the causes of migration. And not create more causes for migration.