But it's only a good judgment call if you have the available transit + shopping time, able body, suitable climate, and a single store that has everything you need.

If any of those conditions are not satisfied then it's better economic utility to outsource that entire task and get your exercise and socialization by going to the gym. You can even walk to the gym too. You can outsource almost anything except exercise.

It's still not practical. Humans just walk too slowly.

Let's be realistic here and accept the fact that anything that involves more than 1km of walking one way won't happen for 99% of people.

That's why we have bikes, for distances from 1km to 10-12km (one way).

And only after that should we have cars. Cars should also be reserved for very heavy loads (more than 50kg), groups of people (not single drivers, 2+ people in the car), and various other niche uses.