I don't think this sort of ethnic essentialism is at all necessary to explain Bulgaria's current problems. It seems especially misplaced given Bulgarian Turks and muslims were subjected to ethnic cleansing quite recently, in the decade before the horrors in neighbouring Yugoslavia.
Petko Slaveykov's famous line 'не сме народ, а мърша' was written in 1875. The fact that it's becoming more literally true than he meant it is hardly the fault of the Ottoman Empire.