Galatians 3:28 was not written in ignorance of or blindness to people groups. Paul repeatedly writes about people groups throughout his epistles, and clearly set an example of targeting specific people groups to reach people with the gospel and to plant churches among specific people groups. The point of Galatians 3:28 is that in the Christian fellowship we should strive for equality among people groups, not to be blind to the fact that various people groups exist.