Well, Greeks are not Slavic but the Orthodox Slavic populations certainly view Greek culture (or to be more precise - Byzantine, East-Roman or Roman culture or whatever you'd like to call it) as one of the foundations of their own culture.

We view each other as brotherly nations and there's not much that can change this, just as the Muslim populations on the Balkans view Turkey as their brotherly nation.

The only reason they all signed up for the EU is because of the promise of a better economic future, not because they want to be part of western culture.

During the last years it has become apparent that these promises will not materialize and that's why I expect that the EU will massively contract in the next years.

You got the Bulgaria bit wrong again. Actually Byzantium was Bulgaria's arch-enemy during most of our existence. These sentiments are nor forgotten.

As it was once the enemy of Serbia and Russia.

Bulgaria is today Orthodox Christian and has kept the culture of their "arch-enemy". If the majority of Bulgarians really viewed this as their arch enemy then they probably would have rejected this culture the same way that they have rejected the culture of the Turks (by the way in a extremely cruel way) after they regained their freedom.

Well, it's complicated on why it happened that way. USSR is one undeniable factor.

What does the Atheist USSR have to do with Orthodox Christian Byzantium? The USSR tried to eradicate all traces of this culture by harsh means. They killed priest on a large scale, destroyed churches and outlawed religious practices.

When they saw it didn't work they basically started to control the church from within with their KGB.