Isaiah 7:14
"Therefore the Lord himself shall give you a sign; Behold, a virgin shall conceive, and bear a son,
and shall call his name Immanuel. By the time He knows enough to reject evil and choose good,
He will be eating curds and honey.
For before the boy knows enough to reject evil and choose good,
the land of the two kings you dread will be laid waste."
It's not Jesus? It's the Jewish nation? This nation will be a "son" and a "boy" and born to a
virgin? (remember "virgin" has many meanings, and no, it's not "young woman" because nearly
EVERY young woman became a mother.) It's a "sign", ie something significant and different.
These verses are even harder to shoehorn into your "Not Jesus but the Jews" theory.
Instead of Jews dying for other Jews and looking down from heaven in satisfaction we have Jews
as a boy (singular) all born to some virgin woman. That's clutching at non-existent straws.
Jesus Himself said Isaiah spoke of Him. In a synagogue Jesus quoted from Isaiah 61
The Spirit of the Lord God is upon me;
because the Lord hath anointed me to preach good tidings unto the meek;
he hath sent me to bind up the brokenhearted,
to proclaim liberty to the captives,
and the opening of the prison to them that are bound
THE JEWS WERE OUTRAGED WHEN JESUS SAID GOD DID NOT BRING THIS
MESSAGE TO THEM.