I suspect the fact that Amazon is so good at food delivery is exactly why Instacart has been able to raise at such a high valuation. Amazon's purchase of Whole Foods, their Amazon Go store, and generally competent execution of grocery delivery has put the fear of $DIETY into all the incumbent grocery chains. They realize that they're late to the game and don't have the internal talent to develop an effective and convenient home-delivery competitor, so they're forced to partner with Instacart, who is hoping to commoditize them.