In fact, Catholics do follow many Jewish teachings, such as the Ten Commandments. Catholic Sunday Masses almost always include a reading from the Hebrew Scriptures and a Psalm response.
The Mass prayer, “Blessed are you, Lord, God of all creation. Through your goodness we have this bread [wine] to offer...,” comes from Judaism.
When a second-century Roman priest said that the God of the Hebrew Scriptures was not the same as the God of the New Testament, the Catholic Church described such teaching as heresy. Jesus was born Jewish and cannot be understood apart from Judaism.
Jesus also preached about a Kingdom of God which is open to Jews and non-Jews (gentiles). The Letter to the Ephesians says that Christ broke down the wall between Jews and gentiles, reconciling both with God (2:11-17).
Some Jewish people accepted that teaching while others did not. Those who did so became Christians, willing to call Jesus the Son of God. Not surprisingly, other Jews felt such a title undermined the absolute bedrock of Judaism, their belief in one God.
For the first 40 years after Jesus’ death, many people thought of Christianity as a group within Judaism. As the Good News spread, so many gentiles were baptized that eventually they became the majority.