When suffering comes, great pressure is exerted on Christians to compromise or ignore parts of their faith. They may be tempted to reconfigure their understanding of their faith to accommodate their friends. This was the situation of the people addressed in the Letter to the Hebrews.
Faithless hearing leads to indifference.
This was a falling away. By now these Christians should have been teaching the Word of God. This is meant to be an absurd thing. These are elementary truths, all things the Pharisees believed. They are about Christ in the same way the Old Testament is about Christ.