Knowing truth does not make one spiritually mature.
Knowing the Bible, even memorizing Scripture, does not make one spiritually mature.
I have known many in churches who have lots of experience with church, lots of Biblical knowledge, but I wouldn’t consider them spiritually mature.
They aren’t self-feeders. They don’t demonstrate the fruit of the spirit. They don’t consider others better than themselves.
Granted, we are all a “work in progress”, but…
A mature Christian doesn’t just know truth…doesn’t just know the Bible.
A mature Christian is striving to live truth.
In fact, a mature Christian is striving to be truth. Truth is a person. Named Jesus.
(Just some thoughts from reading Philippians 2 & 3.)