It's written in Jeremiah chapter 3 , And I will give you pastors according to mine heart, which shall feed you with knowledge and understanding.
Hebrews chapter 5
In fact, though by this time you ought to be teachers, you need someone to teach you
After 20 years the congregation should be teachers of Gods word. Duty of pastor is to train the flocks to be shepherds. Its trade. Sadly, some churches have failed to to prepare their congregation. Some Christians are spiritually dead. I call this cemetery school.
And the holy Spirit is needed to understand deep truth of Gods word and discernment. Yes, it takes many years to study and become teachers of Gods word. There are no short cuts. I studied under pastor for over 20 years. Take care.