Like carride, I have been grocery shopping in the US in a very similar way to Argentina for 30 years, so not buying everything at one supermarket is entirely normal for me. I really enjoy the personal relationships I have built up with a variety of merchants over the years, and there is no denying that there are a wide variety of quality differences between stores.
You pay about the same price, often for mass produced items, and artesanal small batch, it just requires a bit of research.
This article doesn’t discuss the explosion in cheap delivery in the last ten years, which makes it pretty easy to have quality food from many different purveyors delivered to your door, ordering by whatsapp, and paying by transferencia.
This is far less trouble and work than my situation in the US, where costco is a one hour round trip drive in one direction, the good deli an hour rt in another, the good fish markets 20 minutes in two other directions.
The best meat markets, cheese shops, and even organic farmers market stands here will deliver, if you ask.