We are on common ground here. I believe the Scripture we have is not 100% pure and accurate but is sufficiently accurate to serve it's purpose. Does that make sense?
For the same reason I will take issue when you, or others, speak of the Septuagint as if there is such a thing as one pure unadulterated thing.
I suppose you could say that Christians wrote the Septuagint in order to make it "fit" the references made by New Testament writers, but that still doens't explain where did the same writers quote from; certainly not from the Hebrew Bible. So, clearly another set of scriptures existed, which Josephus and Philo refer to as the Septuagint.
All of them are 1st century sources. Ergo, there was such a thing as the Septuagint in the 1st century AD, despite the groundless claims of some to the contrary.
And there was no Hebrew Scripture? What makes the Septuagint your superior, or only, source?
Yes and no. It makes sense that there is no 100% pure scripture, because physical evidence shows that to be so. It makes no sense to assume that it is "suffciently accurate to serve its' purpose" because there is no objective evidence to come to that conclusion except by blind faith (in which case you can't appeal to reason).
The other reason why it makes no sense is what exactly constitutes "sufficient" and how does one measure it in this case?
And there was no Hebrew Scripture? What makes the Septuagint your superior, or only, source?
Alexandrian and other (Greek-speaking) Jews were also "real" Hebrews. What makes Palestinian (Armenian-speaking) Jews "more" Jewish? Why does one Jewish sect (i.e. the Pharisaical Palestinian Jews) have the monopoly on what is "authentic Jewish" scripture?
Even in Israel today the state recognizes two equal but different rabbinates, one Ashkenazi and the other one Sephardic. They even recognize the few hundred Samaritans as "real Jews" as well.
Are we to say the Greek-speaking Jews or the Essenes or the Sadducees were not "real" Jews and their scriptures, which differed from what the Pharisaical version and what the West arrogantly calls "Hebrew" scripture, were not equally Jewish?
What makes the Septuagint more important (not necessarily superior on an absolute scale) for Christians is that the Septuagint is the Jewish Bible quoted in Christian scriptures. Clearly, Christian dogma can only be derived form that version or else there is no consistency.