They ought to grow up. But there they sit, playing in the nursery school of elementary truths. It is sad when we come to a place in life where we ought to be teachers, but we need someone to show us the order in which the ABC blocks go. We lose our confidence because our lack of spiritual growth dulls our hearing. Learning promotes learning.
Ignorance promotes ignorance, especially when it is willful ignorance.
I have also realized that ignorance can also be the greatest motivator to learn, when ignorance is used as a signal for our need to learn. When we willfully neglect knowledge of God's provision for our salvation the darkness of ignorance overwhelms us. The writer wants to lead the Hebrews into a deeper understanding of Christ's priesthood, but their willful ignorance has blinded them. Although he was a son, he learned obedience from what he suffered and, once made perfect, he became the source of eternal salvation for all who obey him and was designated by God to be high priest in the order of Melchizedek. We have much to say about this, but it is hard to explain because you are slow to learn.