That's true about wages (although some are close to South Europe at least). How is that hindering the EU though? Do you mean workers migrating for higher pay? Is that not, economically, beneficial for both parties?

Overall for a country it can be beneficial to have immigrants, but it can be hurtful to low-skilled workers in that country to have to compete against the foreign workers. Higher skilled workers usually have less to worry about as connections, language skills, and industry-specific experience give them an incumbent advantage. I realize one of the founding goals of freedom of movement was to allow workers to be able to move to countries with greater opportunities, and that that is overall a good thing. But politically speaking, how do you ensure that you don't alienate large swathes of the working class, and make sure that their needs are attended to as well? As globalization and technology displace more and more jobs, it becomes very easy for people to fall into the trap of joblessness. They then fuel the radical right movements that are springing up across Europe.

This is a conundrum indeed, managing the line between what makes sense (economically or otherwise) and what's acceptable to an population. The coming wave of automation related job displacement is gonna make immigration related job loss look like a small thing. I keep getting back to (forms of) basic income when thinking about how these scenarios would play out.