You meant, "we reject their belief that Jesus was (not) the son of God.<quoted text> Catholics/Christians don't "reject" *Judaism*,we reject their belief that Jesus was the son of God.
The NT is the fulfillment of the OT.
But from THEIR POV, Christianity rejects Judaism, BECAUSE we believe JC is the Son of God.
They don't believe the Messiah has come, yet. They are still waiting.