Some Christian denominations like to argue that they
don't rely on tradition or teachings from the apostles, but they do,
they just don't realize it. Here is a list some of the unrealized
traditions in the church:
-Look of Christ: Why does everyone depict Christ as a lean man with long brown hair and a beard? Why not clean shaven? Or black hair? Or why not overweight? Christ's appearance is not found in the Bible but has been passed down through holy tradition by being represented in icons of the church.
-Use of the Cross: Why do all Christians use the cross as their symbol for the religion? While the cross obviously references his crucifixion and conquering of death, the cross wasn't used a symbol of Christian power until Emperor and Saint Constantine established it in the early 300s.
-Use of the word Trinity: How many times is the word trinity used in the Bible? Zero. The word trinity was first used on record around 181 A.D. by Theophilus. He was backed by other church fathers and authors included Tertulian and St. Irenaeus. St. Irenaeus is notably known for his book "Against Heresies", written in the 2nd Century. His book appears prophetic as he counters claims that, from a modern perspective, would not appear to gain traction for another 1400 years.
-The date of Pascha (Easter) and Christmas: Why do all Christians generally celebrate Easter and Christmas at the same time? These were dates established by the early church based on a liturgical calendar. Many modern Christians have thrown out all the other important feasts and celebrations of the church but kept what they view as the two big ones. Of note, based off following the Gregorian or Julian calendar there are sometimes differences in the dates of these holidays between Orthodox and Catholics.
-The Church of the Holy Sepulchral aka Church of the Resurrection: Christians from all around the world agree on the site of the crucifixion and resurrection, why? This is a holy site that was passed down via oral tradition for the first couple of hundred years until St. Helen (St. Constantine's mother) went to Jerusalem to identify the site and begin the process of building a church on the grounds.
-The name "The Bible": Why do you call the book, The Bible? The Bible was a name first recorded on paper by St. John Chrysostom who referred to the writings as "Vivlios" (transliterated), which in Greek looks like Biblios meaning "The Books". He used this term in a homily on Matthew circa 387. As the documents that became the Bible were made into a single book instead of multiple books it became The Book or The Bible.
-The Books in the Bible: How do we know what books belong in the Bible? The books of the Bible are no doubt divinely inspired but these books were bound together by men. The first written record of all the books of the Bible is from the 4th Century by St. Athanasius. The oldest Bible is the Codex Vaticanus from the early 4th Century. While there might be some variation among denominations, most of the Bible was agreed upon by early church fathers and that tradition (teaching) was passed down to you and I today.
-The Order of the Books in the Bible: Why does every book start Matthew, Mark, Luke, John, Acts and then into the Epistles? Why not re-arrange the books and move John earlier? Tradition passed down the order and we maintain that order today.
-The Lord's Prayer: Why do you recite the Lord's Prayer from the book of Matthew and not the version from Luke 11:2? There are slight differences but everyone uses Matthew instead of Luke. This is from Holy Tradition that has been passed down. Many that are reciting the Lord's Prayer don't even realize they are using Holy Tradition but they are.
-What is a heresy?: Most major Christian religions agree on heresies fighting against topics like Arianism, Nestorianism, Monophysitism, Docetism, Marcionism and more. How do we know these are heresies? They go against teachings of the Bible established by the early church fathers. If it is "solo scriptura" or just you and your Bible, then an argument can easily be made that these are valid opinions.
The list can go on but the Orthodox Church provides continuity via apostolic succession dating back to the time of Jesus Christ. Google "Timeline of the Church" and images like the one below will come up.