This is not a coincidence - it is part of their placement strategy. They look for low income locations with cheap real estate which they can dictate terms.

https://www.forbes.com/sites/laurendebter/2022/05/20/dollar-general-opening-new-stores-across-small-town-america/?sh=20020265ce5f

Make your own is the answer. Real vegetables (unprocessed and typically raw), fresh meat, and sometimes fruit. Your dog will be much happier although it takes a bit more work preparing and storing compared to kibble.