Actually NO, I don’t think you are getting it. The OC encapsulated in the Law was not Israel’s doing but God’s, but by Israel’s hand the law was weakened (Rom 8:3) through disobedience and so its demise ensured; not due to the law AND commandment being bad (Rom 7:12) but that it could never bring righteousness. The TWO covenants symbolised in Sarah/Isaac and Hagar/Ishmael were of GOD, not man… how you can deny this staggers me. One however ultimately wrought death/condemnation (2Cor 3:7, 9) by the nature of it being law, and thus their faithless inability to live up to it; but the other breathed LIFE — that’s the contrast.
I just don’t see how this has anything to do with the reconciliation of humanity.
I accept your inability to see this, that is plain, but for sake of making it plain to others let me explain. Pantelism answers this way…
Of all peoples, God chose innocuous and insignificant Israel to be His servant priests and the means whereby He would bless the world. Through many sins Israel abrogated her calling and came under severe judgement… from this she needed redeeming — ultimately this occurred through Christ. Israel needed redeeming to fulfil her mission to be the means of divine blessing to the world —** again this was ultimately fulfilled through Jesus and his Body of ‘firstfruit saints’.** With Israel redeemed reconciliation could then flow unhindered to the world beyond… God’s blessing to all. Paul writes of it this way…
Rom 11:12, 15 Now if their (Israel’s) fall is riches for the world (humanity), and their (Israel’s) failure riches for the Gentiles (firstfruit saints Acts 13:48; 15:14, 17), how much more their (Israel’s) fullness! … For if their (Israel) being cast away (by God) is the reconciling of the world (humanity), what will their (Israel’s) acceptance (by God) be but life (redemptive resurrection)* from the dead?*
Thus did Israel’s redemption reconcile the world — to quote somebody really important… “it is finished!”