I'm kinda hoping that the current concept of urban cores will be replaced substantially by "fifteen minute cities" or whatever the term is.
However, I think there are logistical problems with economies of scale, with supplying a large number of small grocery stores versus a small number of centrally located large grocery stores. Things like that.
The grocery store question is interesting.
In recent times, there were widely published shortages in Australia of fruit and vegetables.
I didn't notice them.
The reason is simple. Big supermarkets rely on centralised warehouses and all product is shipped into a warehouse, and then shipped back out again.
This process wastes resources, for example, you can buy produce at Woolworths in South Australia, that was grown here, driven to Queensland, and then driven back to the local store. That's a lot of diesel fuel consumed for no reason (except enabling the supermarkets to force farmers to sell at the supermarket's price). The time it takes to do that pointless trip also reduces quality, and there is some spoilage that is written off.
Local greengrocers rely on local markets, which rely on local producers.
Some local greengrocers rely on a scheme where back-yard growers sell their produce to the local store.
Somehow the local system is more resilient, than the centralised system, and we didn't see any of the national shortages in our local (non supermarket) stores.
Some of the supermarkets were starkly under-provisioned though.
My state does have a lot of 'market garden' producers, but I would have thought we were very small in terms of the national market.
Edited to add:
Sorry, I forgot to mention that I shop at a local greengrocer, that may not be clear from the above.