Well ... you've just agreed with me. The full context is (Romans 9:3-8)
3 "For I could wish that myself were accursed from Christ for my brethren, my kinsmen according to the flesh:
4 Who are Israelites; to whom pertaineth the adoption, and the glory, and the covenants, and the giving of the law, and the service of God, and the promises;
5 Whose are the fathers, and of whom as concerning the flesh Christ came, who is over all, God blessed for ever. Amen.
6 Not as though the word of God hath taken none effect. For they are not all Israel, which are of Israel:
7 Neither, because they are the seed of Abraham, are they all children: but, In Isaac shall thy seed be called.
8 That is, They which are the children of the flesh, these are not the children of God: but the children of the promise are counted for the seed."
In the bold it is TWICE shown who Israel are - (i) Paul's kinsmen according to the FLESH, and (ii) sons of fathers who ACCORDING TO THE FLESH Christ came. That would be Abraham, Isaac, Jacob and JUDAH. That is, ISRAEL is OF THE FLESH. Verse 6 then CONTRASTS an Israelite with a "child of God". The grammar is clear. There are SOME who "ARE OF ISRAEL", but something happened and they are no longer Israel! How can this be? BECAUSE THE EXPERIENCE A NEW BIRTH VIA THE HOLY SPIRIT. This makes the "one-time Israelite" an Israelite NO MORE - but a Child of God. Just answer the question for yourself. WAS Peter the Apostle an Israelite? YES!. But IS he now an Israelite? NO! He is a NEW CREATURE (2nd Cor.5:17). And in this NEW MAN is NEITHER JEW ....! (Gal.3:28; Col.2:11).
Take Paul then. Verse 6 says, Paul ... OF ISRAEL ... is (NOW) NOT ISRAEL. What happened? The New Birth which makes a NEW MAN which has NO JEW and NO GREEK. Paul WAS Israel, but is NOW not Israel.
Verse 7-8 then gives an analogy. Abraham brings forth seed by the FLESH with Hagar. Sarah is BARREN. So the Holy Spirit must INTERVENE. Ishmael speaks of Israel according to the FLESH, and Isaac is the seed of promise which came by the intervention of the Holy Spirit.
The CONTRAST THEN is;
One company of men called Israel - born of the fathers
One company of men called "sons of God" - born by the Spirit