Once, when I was a kid, a person joined our parish with the declaration, “I am here to save the parish!” It was seen by some that we had to stop being who we were and be made in some new model of the 1970s. The music had to change. The way Mass was celebrated had to change. The was CCD (now PSR) was taught had to change. And in many ways they were correct. In one crucial way they were wrong. We couldn’t stop being who we were. It should have been a fulfillment of who we were. Instead, it appeared to be a mentality of “old is bad” and “new is good.” It was not a development of who we were, it was an instant and complete makeover.
The advent of the New Testament paid for with the Blood of Christ is not an inhalation of the Old Testament, it is a fulfillment. The Old Testament is a building up to the NT and something that helps us understand it better. Conversely the NT helps us understand the OT better by enlightening us further as to what God was trying to say through the law and prophets. With both lenses of the binoculars we see better.