1. I can't see the produce/meat/seafood and pick the pieces I want. They aren't all the same, so this matters.
2. I can't get beer or wine delivered, and if I need to go to the grocery store to buy it, I might as well buy all my other groceries while I'm there.
#1 is probably not solvable. #2 is solvable but the US has 50 different state liquor law regimes, so it's a bit of a challenge.
So I'm not really surprised that Amazon isn't doing that much better than the others. Amazon is good at delivering things, but groceries aren't good things to deliver compared to the other stuff Amazon sells. Whole Foods in particular caters to shoppers who care about the quality of their meat and produce and want to examine it before they buy.