The books of the New Testament specifically do not include a table of contents or index as to which other books are valid and apostolic, but is rather a collection of Apostolic writings. Additionally, the books of the New Testament do not comprise, nor were they intended to comprise, a liturgical manual or a book of church order.
We in fact have two books of church order from the first century, at least two liturgies that date from at least the second century and are probably older, a third century book of church order which also contains liturgical text, and in the fourth century the oldest extant complete Bishop’s euchologion or service book, as well as another book of church order which contains more liturgical texts, and at least two additional liturgies.
I referred you to many of these months ago.
And it is not a question of omission by our Lord or the Apostles, but rather this pertains to the distinction between those things which were initially kept on the basis of oral tradition and those things which were important enough to write down.