Let's not overstate the case. The EU was built to keep France and Germany from getting into another war, and it has been successful at that. All the other "principles" are just window dressing.
I'm not defining anything. I'm just explaining why the key decision makers actually created the EU. The statements made for public consumption shouldn't be taken too seriously.
Simplistic reply without substance. The EU economic growth is influenced by much more than just the integration. It can be stagnant not because but despite the integration. It could also be the case that EU integration was an attempt to improve economy but it didn't work out.