What is the Orthodox answer to sola scriptura?

When Christ established the church, there was no scripture for 300 years. The New Testament was not codified for 300 years. Not 50 years, not 30 years, 300 years. So what did people do for 300 years? They went to church. They received the Holy Eucharist. All of our historical documents show us that from the very beginning we have always had the church. And what did Christ give us in the church?

He gave us the sacraments: baptism, chrismation for the receiving of the Holy Spirit, confession for the remission of sins, the Eucharist for the deifying of our souls and bodies, the healing of our soul and body. These are the things Christ gave us. There was no such thing as I am a Christian but I do not go to church, maybe until 50 years ago.