I understand from your studies that there is an age of accountability yet, there are many scriptures that seem to say otherwise. For instance, Paul recognizes that “all have sinned and fall short of the glory of God (Rom 3:23).
The problem I have with age of accountability is, we are born in a sinful condition due to Adam and Eve (Gen 3:6-7; Rom 5:12) David described it this way; “Surely I was sinful at birth, sinful from the time my mother conceived me” (Psalm 51:5). This implies that even in the womb we are guilty. How do we reconcile this with Paul inferring an age of accountability?
These are two different issues. It is true that children under the age of accountability are sinners because as David wrote we are conceived with a sin nature. But until children are intellectually mature enough to understand the nature of sin and its consequences, God does not hold them accountable for their sins.
This is why Paul could say, “Once I was alive apart from the Law, but when the commandment came sin sprang to life and I died” (Romans 7:9).
Like all of us, Paul was born with eternal life and began his life apart from the law. But when he became mature enough to understand about sin, he became accountable to the commandments. At that point he was scheduled for death.
Jesus said we can’t enter the kingdom unless we become like little children (Matt. 18:3). That means unless we return to a state where we’re not accountable for our sins. That’s what being born again does for us. Paul described this in Romans 7:18-20.
David understood this, too. In Psalm 32:1-2 he wrote, Blessed is the one whose transgressions are forgiven, whose sins are covered. Blessed is the one whose sin the Lord does not count against him and in whose spirit is no deceit.