There is often an appeal to the Septuagint as authoritative for canon. Few problems with that. First, who decided what got in the Septuagint? Secondly, we know the Apochrypha wasn't a part of the original the translation was made before they were written. So they were added, it's a pretty big assumption to assume they were a part of it during Jesus' time. So the assumption that the Septuagint was always just like we see it now or even was as we see it now in Jesus' day is a huge leap, one which I think more evidence is against than is for.
There is also some evidence that part of the reason that the New Testament quotes the Septuagint so accurately in so many places has to do with there being some alteration of the text over time. It is really quite possible the agreement is not nearly as strong in the original Septuagint.
Of course we also have the thing that the Jews did not recognize them. They did not officially designate a canon until after the destruction of the temple, but that doesn't mean it did not exist, they wrote all sorts of things down then because they were afraid it would all be lost as the people scattered.
It's interesting that the Pharisees were the forerunners of the rabbidical system and it's really that group that would have been the ones to designate the Jewish Canon. It's interesting because Jesus said something rather remarkable about them considering all his condemnation of them. Here it is:
Mat 23:2-3 NET. "The experts in the law and the Pharisees sit on Moses'seat. (3) Therefore pay attention to what they tell you and do it. But do not do what they do, for they do not practice what they teach.
Jesus told the people to pay attention to what the experts in the law and Pharisees taught, those groups never recognized the Apochryphal books. The group of Jews that might have, were the Sadducees, a group of high up heretics.
Act 23:8 NET. (For the Sadducees say there is no resurrection, or angel, or spirit, but the Pharisees acknowledge them all.)
So I don't think it is too wise to take the teachings of the Sadducees too seriously, but the Pharisees and the experts in the law, Jesus said their teaching were to be paid attention to.
Now some want to say the Jews shouldn't be listened to on what is scripture, but let's be real for a second. How would we know if most of the Old Testament was or wasn't scripture if we didn't follow the Jewish canon. We really wouldn't have a clue, everyone follows the Jewish canon, right up until they want to disagree and then they appeal to some sort of superiority. Well in Romans we are told the Jews were entrusted with the oracles of God (3:2). It was kind of strange, but the Jews always recognized God's prophets even though they had a bad habit of going against what the oracle said or even killing the oracle. They never recognized the people who wrote the Apochryphal books as oracles.
Now look where everyone who accepts them puts them. In the Old Testament, into the time before the church, they are clearly not Apostolic so to be scripture, they must be Prophetic. Yet from Malachi until John the Baptist, no prophet was recognized.
Malachi fortold the coming of a messenger of Elijah.
Mal 3:1 NET. "I am about to send my messenger, who will clear the way before me. Indeed, the Lord you are seeking will suddenly come to his temple, and the messenger of the covenant, whom you long for, is certainly coming," says the LORD who rules over all.
Mal 4:5-6 NET. Look, I will send you Elijah the prophet before the great and terrible day of the LORD arrives. (6) He will encourage fathers and their children to return to me, so that I will not come and strike the earth with judgment."
John the Baptist was that messenger, that Elijah.
Mat 11:10-14 NET. This is the one about whom it is written:
'Look, I am sending my messenger ahead of you,
who will prepare your way before you.' (11) "I tell you the truth, among those born of women, no one has arisen greater than John the Baptist. Yet the one who is least in the kingdom of heaven is greater than he is. (12) From the days of John the Baptist until now the kingdom of heaven has suffered violence, and forceful people lay hold of it. (13) For all the prophets and the law prophesied until John appeared. (14) And if you are willing to accept it, he is Elijah, who is to come.
The apocryphal books basically came between those two books, Malachi and Matthew. Thing is, while they share Jewish history and culture with us, they really don't have anything to do with the story about Jesus. They are just this sidebar not written by prophets.
In the end, I think the arguement has to come down to 1. whether to accept what the Jews recognized or 2. whether to accept the teaching by those who claim authority that their authority extends back to a time before the Christian church even existed or 3. Accept the Septuagint due to quotes in the New Testament with a couple huge assumptions of it being as we see it now, then, and that the people then accepted everything in it as scripture.
The early fathers predominately favored the same 22 books the Jews had, this extended pretty much right up till Jerome, though there were certainly as time went on people who accepted additional books. It was one of those quirks of history, that Jerome, who did not accept the apocryphal books himself, when he gave in and included them in the Vulgate, though he didn't even bother to translate them himself, but simply took old Latin translations, when he did that and the Vulgate became the bible of the Roman Catholic church for basically 1500 years, that act guaranteed their acceptance as scripture in the Roman Catholic Church. The couple he didn't include, they didn't accept, even though the Orthodox church, following the Septuagint of their time did.
So you end up with three Old Testament canons and they really came three different ways. The Protestant accept the Jewish canon, the Catholics ended up accepting the Vulgate, and the Orthodox (most of them) ended up accepting the finished Septuagint, not the original Septuagint. Many Catholics have come to appeal to the Septuagint as their authority as well but that seems to me to be a confusion of history. The Roman church did not use the Septuagint and if it was their authority, their Old Testament canon would agree with the Orthodox, which it does not.
People write whole books on this. I'll stop before doing so. Hope that helps your thoughts on this.
Marv