We never had a perfect world. Genesis 2:9 makes clear there is evil in existence from the beginning. “The tree of knowledge of good and evil” alludes to this. The Hebrew word for “evil” comes from a root meaning of “broken” or “shattered.” God’s creation is the best possible goodness where the brokenness of evil is allowed.
Why allow evil? Its existence makes the existence of chosen relationship between people and God possible. Without the possibility of separating from God, how would a freely chosen loving relationship be possible?