Implicit in all non-Catholic doctrine, or the vast majority of it, is the basic belief that no, God didn't do just fine with the Old Testament. Either the Septuagint erroneously included books that should not have been a part of the canon but were included in the canon right up until Luther, or everyone who has come along since Luther has discarded legitimate portions of the Scriptures. So if you're non-Catholic, then you by definition do NOT believe that God "did OK with the Old Testament".
So, was the Septauigent in error but both Christ and the Apostles didn't bother to mention the fact that the most common version of the Scriptures in use was incorrect or did Christ and the Apostles a) not think what was or was not a part of the canon was important, or b) agree that what was included in the Septuagint was all a valid and inspired portion of His Word?
Christ and the Apostles obviously, "acknowledged" Scripture that non-Catholics have determined they shouldn't have. Hopefully those who do the "acknowledging" on behalf of non-Catholics have set Christ straight by pointing out to Him that although He is the Word, He didn't acknowledge errors in The Word that was in common use while He walked the earth. I guess after a good talking to from Luther Christ will know not to make that same mistake again, right?
“So, was the Septauigent in error but both Christ and the Apostles didn’t bother to mention the fact...”
If you read the words of Christ and the Apostles, it would be obvious they accepted what is now called the Old Testament, and did not include the entire Septuagint as scripture.
Nor did the Catholic Church, on the whole. The Apocrypha was held as good for reading, but not authoritative for doctrine by much of the Catholic Church until the Council of Trent overruled that position in the 1500s. That is why Luther’s accuser told the Pope that the Apocrypha was not useful for doctrine.