A lot of your complaint is based upon where DG's are located. Do you have more info beyond your country? There's quite a bit of variance on density state to state and county to county, from what I've gathered.

One thing I've done is taken a look at proximity of DGs (or DG Markets) to Walmarts (or FDO), plus taken a look at traffic and how it relates to distance from a Wal-Mart, via various random samples, using: https://analytics.placer.ai/

My findings are too ad hoc to report out, but throw me a state and suggested area and I'll try to come up with something intelligible if I find the time.

FWIW, I do think your right that one DG strategy for denser areas has been to go the DG Market route, which draw more (low margin, food heavy) traffic than regular DGs, especially when Wal-Mart has a closeby location. But my rough data also suggests the 3/27 is probably an outlier county, and is on the poor end of DGs/DGx/DGMarket etc staying away from Wal-Mart.