Orthodox Priests in 1800's generally had access only to an elementary education. Some self taught, advanced on their own beyond that, but they were not the norm. The only access to a higher education beyond the elementary level for slavs would be to travel to the west, which wasn't an option for many. Some were reportedly able to afford to make the trip.
The Union of Florence became fully inoperative as soon as the Turks occupied Constantinople (1453). In 1484 a council of bishops condemned it officially. Neither the sultan nor the majority of the Orthodox Greeks were favourable to the continuation of political ties with Western Christendom. The Byzantine cultural revival of the Palaeologan period was the first to experience adverse effects from the occupation. Intellectual dialogue with the West became impossible. Through liturgical worship and the traditional spirituality of the monasteries, the Orthodox faith was preserved in the former Byzantine world. Some self-educated men were able to develop the Orthodox tradition through writings and publications, but they were isolated exceptions. Probably the most remarkable among them was St. Nicodemus of the Holy Mountain, the Hagiorite (1748–1809), who edited the famous Philocalia, an anthology of spiritual writings, and also translated and adapted Western spiritual writings (e.g., those of the Jesuit founder, St. Ignatius of Loyola) into modern Greek.
The only way for Orthodox Greeks, Slavs, or Romanians to acquire an education higher than the elementary level was to go to the West. Several of them were able to do so, but in the process they became detached from their own theological and spiritual tradition.
Peter the Great (1682–1725) -- was not a supporter of the Orthodox Church. He vastly increased the power of the Czars over the Russian church. When Patriarch Adrian died, Peter blocked a successor being appointed. Instead he the Tzar would appoint all bishops. A the Holy and Supreme Synod was established to govern the church, instead of a single Patriarch, and it would remain this way until 1917.
Under Peter: "A clerical career was not a route chosen by upper-class society. Most parish priests were sons of priests, were very poorly educated, and very poorly paid.".
The late 18th century influential spiritual revival in the Russian Orthodox church. The rise of starchestvo under Paisiy Velichkovsky and his disciples at the Optina Monastery. This revival did not address the education or more specifically lack of formal education of most priests.