> It's also true that any country in the EU can choose to leave the EU at any time, 

Exactly. If countries want to be 100% sovereign, they can do a Brexit and enjoy the benefits and the downsides of doing that.

This {$x}exitter bullshit is so tiring. 27 space programs, 12 types of fighter jets etc are horrible expensive. EU-countries enjoy super-high benefits of sharing burdens. In times of might makes right, it gives each a high degree of sovereignty for a steep discount. Yes, being part of a collective does mean that you have to give-and-take with the collective.

It isn't a game of all "benefits for me" in a zero sum game.