Romania, Serbia, "Macedonia" (yes, the quotes are intentional, and yes, I know it's not cool, and yes, this is pretty typical), Bulgaria - they're all on a completely different level of human development, corruption, values, etc.
Part of the reason is 500 years of Ottoman rule, another part is the close proximity and close relations with the Russian Empire/USSR/Russia, but someone who's Czech or Hungarian or a Croat is much closer culturally with someone from Germany/Austria than someone from Bulgaria is.
Being part of the Austro-Hungarian Empire and part of the Ottoman Empire completely changed how those countries developed, and the situations they're in now, even though countries are sometimes only hundreds of miles apart.
Hungary, Czechoslovakia had revolutions, in '56 in '68 respectively, to attempt to escape the iron grip of Mother Russia while a large portion of Bulgarians to this day are Russophiles and nostalgic about those days, not to mention EU- and NATO-sceptics.
Props to Western Europe for literally dragging countries like Bulgaria and Romania and Serbia away from the clutches of the Russian Bear and into Western Civilization, but I'm not convinced they'll be successful.