No - in that God very often does use many other ways to get through to people. It does not all happen in a formal church setting - which what we generally think of when we speak of preaching, Lord's Supper and baptism. Think again of the workshop. Say a furniture making shop. Different pieces of furniture require different tools.
Different woods require different approaches.
In God's workshop, where faith is shaped in different people, different tools are used. Preaching, Lord's Supper, and Baptism are the three mainstay tools. One more important thing to note - Notice that the questions and answers of the Catechism focus time and again on the completed work of Jesus Christ. They tell us that the sacraments point us to that. In other words - they are no good by themselves.