Having stayed with friends in Gwinnett County (now living in Cherokee County), I would concur that it has mostly been ruined by Fulton and DeKalb County ghetto trash. My friend now calls it “DeKalb County East”.
Cherokee County is well on the way to becoming the next Cobb & Gwinnett unfortunately, but I agree with your post.
East Dekalb is Rockdale County. Your friend should probably call it North Dekalb.