My platinum Amex works at Walmart just like everyone else's credit card, and with curbside pickup, I don't even have to go in. I can pull up, check in with the kids still in the car, and have the car loaded and be on my way in 5 minutes.
I don't shop Whole Foods because a) the value isn't there ("Whole Paycheck", and I don't have nor want Prime to get a discount) and b) Walmart is a slightly less evil sweatshop than Amazon (IMHO).
Sidenote: If anyone from Walmart Labs is reading this, you've really up'd your mobile (iOS) game. Kudos.