You made a good point: “Not only can we show it was practiced by the Jews of the time of the Maccabees, but it has even been retained by Orthodox Jews today, who recite a prayer known as the Mourner’s Kaddish for eleven months after the death of a loved one so that the loved one may be purified.”
Thus we go back to the Old Testament for proof of praying for the souls of the dead and I accept that.
We won't debate if 2 Maccabees is canon or not as the Jews rejected it and it was not considered canon by the early church.
Thus we go back to the Old Testament for proof of praying for the souls of the dead and I accept that.
We can go back to the OT and see sacrifices being made in the Temple....doesn't mean we should do them today.
What we do have is this from the New Testament being addressed to a primarily Jewish audience.
Therefore it was necessary for the copies of the things in the heavens to be cleansed with these, but the heavenly things themselves with better sacrifices than these. 24For Christ did not enter a holy place made with hands, a mere copy of the true one, but into heaven itself, now to appear in the presence of God for us; 25nor was it that He would offer Himself often, as the high priest enters the holy place year by year with blood that is not his own. 26Otherwise, He would have needed to suffer often since the foundation of the world; but now once at the consummation of the ages He has been manifested to put away sin by the sacrifice of Himself. 27And inasmuch as it is appointed for men to die once and after this comes judgment, 28so Christ also, having been offered once to bear the sins of many, will appear a second time for salvation without reference to sin, to those who eagerly await Him (Hebrews 9:23-28 NASB).
The message of the NT rejects the concept of purgatory.