There is a perception that only the "professionals" need to study the Bible. Study of the Bible is left to the hired guns: seminary professors, pastors, priests, etc. These people are expected to feed us, with no effort on our part. This is somewhat of a throwback to the Medieval Catholic approach to the church, which was that only the church officials could be trusted with the Bible. If you didn't speak Latin, you only got the Bible second-hand. The priests were there to explain the Bible to the lay men. Several Godly men challenged this, believing that the scripture was for everyone. Some were excommunicated and under constant threat of death, such as Martin Luther. Others were killed - William Tyndale was burned at the stake for daring to produce a Bible in English.
And yet, many Western believers today rarely open a Bible. Instead they rely on Sunday morning sermons and social media influencers. This is fine for spiritual newborns. But even toddlers can feed themselves. A believer who has been saved for years, but only gets fed by others, is like an adult being spoon-fed because they are unable to feed themselves. This would be deplorable in the physical realm; how much more is it in the spiritual life? Christians who are only fed by others are unaccustomed to solid food, only able to tolerate food that has been pre-chewed by others.
The reason brave men worked to bring the Bible to the common man is because when the scripture is hidden behind "experts", those experts can twist the scripture and there is little recourse for the lay people. How will you know if you are being told something heretical by someone you trust unless you have the source - the Bible - available to counter false teaching? But having a Bible is of no use if you don't use it. Far too many people are willing to trust teachers who have smooth delivery, charismatic presence, and social media followers, without any regard to whether or not those people are actually speaking the truth. This is true in many fields from history to science, but is especially egregious in the realm of Spiritual truth.
"Doctrine" sometimes has a bad connotation. It is associated with unreasoned dogmatic stances. But doctrine is important. Doctrine means "what is believed". We all hold to certain doctrines - that is, beliefs - about God, the Bible, and ourselves. The reason why what we believe is important is because we always act in accordance with what we believe. If you believe you are ugly, you will act accordingly. If you believe you are a child, you will act like a child. If you believe that you are a new creation in Christ, you will tend to act out that truth. This is why it is important to have proper doctrine. If you have faulty doctrine, you will live in faulty ways. The closer your beliefs align with God, the more Godly you will be. And vice versa.
And how do we develop correct doctrine? By studying the Bible. If you have no interest in learning more about God and improving your relationship with Him, you have other issues. But if you want to grow spiritually, the only way to do that is to study the Bible, which is God's revelation of reality to man. Without it, sin warps our view to the point that we don't actually perceive reality: we emphasis the unimportant, we treat people like things, we treat things like God, we enslave ourselves to addictions, and we are easily led further astray by others. Because of sin, we cannot detect when people are mixing lies with the truth. The Bible is the solution to this. But you have to study it.
Finally, some would say that this is an over-emphasis of the Bible. After all, the Holy Spirit will lead us into truth, so all we need is the Spirit. However, the Spirit does not usually operate in a vacuum. The Bible provides the material that the Spirit will use in your life. Consider places where the Bible is not available. Many heretical beliefs spread in Africa in places where the Bible was not available to believers. They were saved. They had the Spirit. They had fellowship. They prayed. They had faith. But many fell into error because they did not have the Bible available to correct them. Many of Paul's letters were to correct churches that had started to go astray despite the fact that they had the Spirit, and had been taught by Paul himself (sometimes for years). Countless heresies have started among people who did not have, or did not heed, the scriptures. So don't think that somehow all you need is just "you and God." He gave us the scriptures for a reason. If we foolishly neglect what God has provided, we can expect to suffer the consequences.
Note: by the foregoing, we are not saying that you don't need the Spirit. Having the Bible without the Holy Spirit to guide your understanding is worse than having the Spirit without the Bible. The Bible is spiritually discerned and one cannot expect to benefit from its study without the presence of the Spirit dwelling in the heart of the one studying. That is the way of the Pharisee.