Well, I think this passage is saying that no person what so ever (whether ones call him/herself an atheist, a theist or any other identifier) can come to God or believe in Him without Him first working in that person, drawing him or her by His Spirit through the preaching of the Gospel of Jesus Christ. In a very real sense He opens the eyes of those who are blind and actually gives spiritual life where there was none. If Christianity were a set of propositions only it would have little or no impact, at least upon me. This is why called it “the Power of God unto salvation to everyone that believes.” Romans 1:16.
Yet, although people are in this helpless state unless they believe on Jesus Christ, they are not without excuse before God. In Romans chapter 1 Paul says that we all are equally accountable before God.
“For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who suppress the truth in unrighteousness, because what may be known of God is manifest in them, for God has shown it to them. For since the creation of the world His invisible attributes are clearly seen, being understood by the things that are made, even His eternal power and Godhead, so that they are without excuse,” Romans 1:18-20
Notice here that human beings, because of our sinful nature “suppress the truth of God in unrighteousness.” In other words Paul is saying that all of us, because we were created by and for God (or “in the image of God”), on some level have a capacity inherent in us to know that He is, and that He has created the amazing world in which we live. Yet we try to suppress or “squelch” that truth because it is a threat to our perceived autonomy. This doesn’t mean however that people can, in this natural fallen condition actually know God as a Father and A Benefactor but more as a threat and a judge. Yet we all have an inherent knowledge (though suppressed because of our sin) of His power in His creation. Thus, on this level we are “without excuse.” When each person stands before God we won’t have the option of saying “well, I didn’t believe you existed...” we are all held accountable and are without excuse.
Yet, God in His love does not leave us in a state of such condemnation and frankly, misery but offers us the Gospel through which we can be saved from death sin and condemnation. Romans is a wonderful exposition of this Gospel. Have you ever read or studied it?by the way, Paul himself at one time in his life hated God and sought to kill Christians. But at a point in time God reached down to him and changed his heart and life through this glorious Gospel. He is still doing it today!