You don’t have to tear it all down. Just tear some of it down. For example, you could tear down a single house and replace it with a shop, and suddenly a whole neighbourhood would have a shop within walking distance.
I wonder where people live that this isn't already true. My suburban neighborhood has several small & medium sized markets. I have a suspicion that many HN participants idea of suburbia is the endless tract housing variety. That's just one version, and comparatively rare in my region. Our suburban neighborhoods are mixed.
Suburbia probably doesn't have enough density that the number of people who choose to walk to the shop over driving twenty minutes to the huge shop could keep the small shop alive.