Have you considered that those who are unregenerate already know God, but they know Him as an enemy, not as a friend. Romans 1 declares although they "knew God" they "suppressed the truth in unrighteousness". So they are guilty for rejecting what they KNOW. When they hear us preach the gospel they reject it outright and will not believe because they "love darkness" and "hate the light" (John 3:19). Then the truth that they know and hate is changed altogether by God to a truth that they know and loves. Before that time, unless God opened their eyes and ears, they could neither see nor hear (Deut 29:4, 30:6) because they would not. It is a matter of their love and hate, not a matter of simply having no conception whatsoever of what is being said. They understand the concepts being communicated well enough, they just hate it. How could they be "hostile to God" (Rom 8:7) if they knew nothing about Him?
So if the unregenerate cannot understand God, what is the use of declaring the gospel? When we proclaim the law (and gospel) to unbelievers we do not preach it thinking they will want it, or believe it on their own. No Paul says the purpose of the law is not to show their ability, but to reveal sin.(Rom. 3:19) But we do so always with an eye to God that the things we say will be used by God to convict them as He changes their heart of stone to a heart of flesh, so they will flee to Christ as their only hope. People are not saved in a void but through the gospel. James says, “He chose to give us birth through the word of truth” (James 1:18).
Part of a comment by Patrick Korseck I think will be helpful here: