Bahman,
Your question is a good one, and I think I have one possible solution. God has not failed to convey his message, we have failed to listen to it because of the many distractions and vanities of human life. He does not “force” us to listen because he desires our free choice to obey. God gives each person knowledge of right and wrong, and we intuit his laws, or can learn of them from the Torah. Each of us has a more or less deep understanding of these laws. We know not to lie, not to murder, not to steal, to live in an ordered society, not to engage in disordered sexual relations, not to be cruel to animals, not to worship false gods, etc. (In fact, I think the recent explosion of atheism is potentially a step in the right direction. People are rejecting false gods at an ever increasing pace, making room for a return to the worship of the true God).
God expects us to do what is right, and we all know it. Superstitious religions, the excessive desire for wealth and power, and many other things distract us from this inner knowledge of God’s message, but the potential for each of us to listen to it always remains. God does not expect us to “convert” to a religion to please him, but rather we must become fully alive and ourselves by following his laws. If we have access to the Torah and follow it because we desire to please God, then we can begin to live as “righteous gentiles.” God has created each of us to know him, do what is right, and be good human beings, no matter when, to whom, or where we’re born.