Costco has home grocery delivery too. https://customerservice.costco.com/app/answers/answer_view/a...
It costs more that on the shelf because you are paying for someone to do work for you. Again, how much is your time worth?
Yes, a lot of people love to pick out their own food themselves, and buy in bulk only every couple of weeks, and take it home in their own vehicle. You are one of them, but certainly not everyone is like you. I am not.
The idea of a less car-centric world is to give more options that don't require a car, not to prevent you from using a car.
If the savings in going to Costco is big enough to justify having a car, then one alternative option is to join a car sharing group. Every two weeks, book a vehicle for your Costco run. In effect you're only paying for a day's worth of car ownership rather than 14 days, where most of time the car does nothing.
I also get much better quality meat, fruit, and vegetables from Costco than Waitrose. So this is a total no-brainer for me. The only downside for some is you need more upfront money to shop in bulk, even if it works out to be cheaper.