Atheist is a weird word. It’s a word that basically means: a person that doesn’t believe in God. But, almost everyone is an Atheist. There have been 10,000 gods throughout history. Since everyone doesn’t believe in 99.99% of these, everyone is an Atheist to a large extent.
Believing in God does not absolutely mean that you have to get the name right, because the word God is neutral as far as identity of that God goes. God isn’t a name, but a title that explains an office. You only have to believe in one God as the creator to not be an Atheist. If on the other hand an Atheist was a person who didn’t believe in the existence of YHWH, or a list of other names, then you would have a point.
Of course there are many explanations as to why there are many different names and IDs for this so-called God. One is that they are the same God, but seen in different languages and cultural perspectives. Just as different cultures have different names for White Men when they first laid eyes on them, (Pakeha, Pale Face, Palangi etc) so it could be that God is given different names and who would actually believe that every tribe and nation would actually choose the same name. I certainly wouldn’t believe that.
The Bible has a unique view about this which doesn’t negate the explanation above. The Bible’s central message is of course that men are cut off from God and the job of the Messiah is to bring men back into relationship with God. So this too explains why most men acknowledge God but have a different name for him or argue about his nature. It is answered in the fact that by nature, we do not know God because we are sinners and cut off from his presence. Of course scriptures show God’s plan for man’s redemption, but in a sinful state, men who know that God exists will have all kinds of wild ideas about the God that they do not know.