The Bible teaches clearly that God’s judgment is based on a person’s response to the truth they have received.
“And a servant who knows what the master wants, but isn’t prepared and doesn’t carry out those instructions, will be severely punished. But someone who does not know, and then does something wrong, will be punished only lightly. When someone has been given much, much will be required in return; and when someone has been entrusted with much, even more will be required.” – Luke 12:47-48
God’s response to those who seek to obey the truth they have is the provision of more truth. To those who respond, more light will be given. To those who had, more was given. We can be sure that every person has received adequate light to which they may respond. God’s existence and His power are made clearly evident to all people through creation and through each person’s innate moral judgement or conscience.
Even Gentiles, who do not have God’s written law, show that they know his law when they instinctively obey it, even without having heard it. They demonstrate that God’s law is written in their hearts, for their own conscience and thoughts either accuse them or tell them they are doing right. – Romans 2:14-15
To the one who responds obediently, God will send more light.
His method for sending this light is a human messenger. Paul shares this in his letter to the church at Rome that the solution to the terrible lost condition of people is the preacher who is sent. Ultimately, the problem is not with God’s righteousness, but with ours.