Ummmm. I think I agree with the sentiment, but as expressed it has some problems.
“The core doctrine, which comes from the Bible” simply has too many issues. In 40 C.E., there was no New Testament, so from that perspective, the “core beliefs” for Christians several years after Jesus had died (if they only come from the Bible) had no reference to Jesus, the crucifixion, salvation through faith, or Resurrection (unless you want to include II Maccabees).
The development of the canon was not a swift, sure process even after the books had been written. Look at the size of the New Testament Apocrypha some time to realize that there were many works written that were not chosen by the community of believers as a representative of doctrine.
The whole matter of Purgatory goes directly to the heart of the issue of the Bible vs Doctrine. II Macccabees (along with I Maccabees, Wisdom, Tobit, and several others) was considered Scripture by many members of the early Church. The discussion over whether they were “really” Scripture must address the issue of how any one knows what is (or should be) in the Bible. This results in discussions of (and disagreements about) the creation of the canon and whether one council or another had greater authority for its list of accepted works (or, if you’re a Jack Chick fan, whether there was “real” scripture–unattested except by those who mysteriously “know” it now–that was somehow corrupted by the chrch of Rome).