Greece, under the Ottomans, became a backwater. Russia had a different experience ~ they were beating the Ottomans. The Serbs, et al, also had a different experience.
Still, the Ottomans were really not interested in fostering Christianity. Greece has probably more than equaled the economic might of Byzantium before it ~ as has nearby Turkey, and even the Balkans. But that wasn't the case in the 1920s when large numbers of Greek people came to America. Be kind to your forebears ~ they were struggling with all their might and here you are.
I understand that illiteracy had much to do with the way Greeks in the centuries past may have encountered the church. Certainly this was the case in most non Northern European countries. The populace was dependent on an educated clergy to direct their religious life. This usually amounted to following proscribed rites and cultural regulations. However, the people I am talking about live in the 21st century and have college educations. For them to ignore Scripture is without excuse.