Paul isn't saying never seek justice, but where and how we seek it matters immensely.
The implication here is that the church should have a functional system for conflict resolution. This isn't about avoiding accountability, but about maintaining the integrity and witness of the community. When believers go outside the church to settle disputes, it sends a terrible message to the world: that the body of Christ is dysfunctional or that its members don't trust God's authority within the community. Paul suggests a better way: let trusted, spiritually mature members within the church act as arbiters.