As long as the people involved in making it care about doing a good job (keeping equipment clean, properly monitoring oil, checking on finished pieces periodically to gauge seasoning/greasiness,etc.) ... there's no reason a grocery store can't make good chicken.
I have found similarly to you. Not so much that grocery store chicken is universally awesome -- more that with not much looking around, you can find pleasant surprises.
EDIT: Rouses on Power Blvd near Kawanee in Metairie makes legitimately great chicken -- both bone-in and fingers. Unlike most grocery stores, though, they have gigantic open kitchen, probably 1/5 of the store's floor space. And they do a huge amount of catering.
But yeah ... those Rouses chicken fingers are like three of Cane's fingers nowadays (yep, Cane's have been shrinking).