I simply doubt very much that Orthodoxy “maintains the life of the Church that was in and emerged from the catacombs.” Regardless, I make a distinction between the Word of God recorded in the Sacred Scriptures and “other practices and teachings” that either are (a) not commanded or forbidden, or (b) contrary to the Word of God.

It should be pointed out that this was a sermon, not a treatise, which necessitates simplification in complex matters such as this.

I genuinely appreciate your gentle tone, and apologize for not responding sooner.

The age of the Orthodox liturgy is never given by anyone I know as the basis of Orthodoxy’s claim to be the Church. If this were so Byzantine Catholics using the same Liturgies would be considered ‘equally’ Orthodox, which is not the case.

The latter point is more fitting, though one must be careful not to assume that Tradition is the same sort of thing as was defended by Rome during the Reformation. Orthodoxy, too, agrees that the Pope is not Tradition, or whatever he says is tradition is tradition. Orthodoxy doesn’t treat any of its Patriarchs or Bishops in the same way, either.

Orthodoxy’s claim would be more fittingly – though not exhaustively – based on the opinion that she maintains the life of the Church that was in and emerged from the catacombs – the Church that was able to recognize the Apostolic from the spurious Scriptures. This same Church also practiced and taught many things that are simply assumed to be ‘mere traditions of men’.

It’s a big, complex topic that can be discussed from many angles with many examples. In short though, if the Church that testified to the inspired canon of Scripture also testified to other practices and teachings, shouldn’t they too be honored and received?