Don't get me wrong -- I'm with you that co-branded products like "Only at Target" KitchenAid are pretty much trash but store-brand stuff doesn't really seem that different to me than any other brand on the shelf. Kroger brand pretzels are dope, their Oreo clone is garbage, c'est la vie.
The store has an incentive to stock it's own brand product beyond what the incentive for competitors is. Ie, they are going to carry a competitor either because it's a good product that sells, or the competitor has paid for shelf space (and is betting it's own money that it's product is good).
Neither of these necessarily applies to a store brand. So even if it's between store brand and unknown 3rd party competitor, I'll go 3rd party first.
That said, there are some store brand products that, having tested, I enjoy. It's just usually not worth the 25¢ to me for the gamble.
At this point I'll happily take the Walmart-specific version over the risk of an Amazon supplied product.