This discussion reflects how badly the concept of "tradition" tends to be understood by protestants. In Orthodoxy, "Tradition" doesn't mean, "this is the way we've always done it, so we should never change!" (Although there are some elements "lower-case-t tradition", like kissing the priest's hand when receiving prosphora, or receiving the Eucharist via a spoon, that are practices which developed over time for various reasons, that isn't the type of tradition under discussion here.)
Holy Tradition is the body of teaching passed from Jesus to His disciples, then transmitted from the Apostles to the Churches they founded throughout the world. It is a continuous stream of consistent thought and interpretation and understanding of the Christian faith. This is why, in the disputes resolved by Ecumenical Councils in the first millennium, both sides argued not only with Scripture (which ends in a stalemate, as Protestantism shows, since relying on Scripture detached from any tradition of understanding leads to relativism) but how Christians had always practiced and understood their faith, as reflected in worship and the practice of the Church.
This is why the iconoclasts lost: they could make arguments from slinging Bible verses, but couldn't account for the consistent, largely uncontroversial practice of iconography and veneration over the centuries, which can be identified very early in Christian history. This is why the Arians lost: they couldn't account for Christ consistently worshipped as God if he was just the first and greatest creation as they claimed. This is why Nestorius lost: his faulty Christology was incoherent with Jesus always being understood as fully man and fully God. The development of doctrine in the first millennium was really the process of more precisely articulating what Christians believed to combat heretical ideas emerging over time.
There is an empirical element to this as well. There's nothing to stop slick exegetes from marshalling Bible verses to explain why God is really affirming of "same sex marriage." But for the Orthodox, this is a much harder argument to accept since the consistent understanding of Scripture and Christian sexual morality by the Church Fathers totally precludes any such novelty. We interpret and understand Scripture on the basis of how it's been understood by the Church Fathers and aren't free to make up new interpretations. This principle is followed only selectively by protestants, if at all.
If you can find a time when Christians didn't believe your doctrine, that's a problem, such as for Sola Scriptura, baptism-as-meaningless-gesture, and denial of real presence in the Eucharist. These were nowhere to be found in the first 1500 years of the Church. On the other hand, the Church always believed in the Real Presence, in Baptismal Regeneration, in a sacramental priesthood and apostolic succession. Given the tendency of the first-millennium Church to erupt in huge controversies over issues that probably seem nitpicky to modern protestants ("does Christ have two distinct natures, or are they mixed into one?"), you'd think that something like the establishment of a sacramental priesthood or the Real Presence would generate tremendous controversy and great debate between the innovators and the "Bible-believing Christians," but there is no evidence of this.
Of course, in the case of post-Schism Latin innovations these did provoke controversy with the East, and/or emerged after the Schism, so aberrant practices of Rome are no obstacle for Orthodoxy. Heresy and schism are never silent things that happen oblivious to anybody's knowledge, but always end up generating conspicuous public controversy, as the history of the Church makes quite clear.
This all raises the question of why God would transmit the Christian faith this way when He gave Moses stone tablets with everything clearly laid out. Why not just have Jesus drop off a King James Bible before ascending into heaven?
Remember that as modern people spoiled by printing presses, our perspective is fundamentally skewed. In the ancient world, the written word was slow and expensive. The Christian faith Jesus gave us spread incredibly rapidly throughout the ancient world because it was orally transmitted and could be taught in person. This meant that it took quite some time to get everything written down, especially subjects such as worship and sacramental practice, which would make little sense to emphasize in writing: would you get more value from learning how to conduct a liturgy based on reading a scroll, or learning it from the tutelage and observation of someone who knew it? The answer is obvious. It traveled with the Apostles and those they appointed and allowed for quick and effective evangelization. In contrast, the Mosaic Law was given to a single coherent nation which would occupy a defined geographical region, quite a different situation from the Church, and also functioned a full-blown civil law for the nation of Israel.
So in conclusion, a proper understanding of what Holy Tradition actually is, will clear up many misconceptions surrounding Orthodoxy.
