> Has anyone moved from a semi-dense area where just about anything was within a 10 minute drive, to a situation where they didn't use a car and still lived a decent efficient life?

I used to live in Sante Fe, New Mexico in the US. The city was founded in 1610. The city core for the first 300 years was of course walkable, but the last grocery store downtown closed around 2000 so it's a mile walk to the nearest store (biking isn't really an option in Santa Fe).

When I lived there the population was about 65K. I lived in a post-war suburb about a 30 minute walk from the center of town. When built it was on the outskirts of town, connected to downtown via a gravel road. It's all paved now, and a great place to live with a car as just about everything was a 10 minute drive away (though I would need to pay for parking downtown).

The city extends many miles away from the center of town. Going along Cerrillos Road you can see the effect of zoning changes over time. In the center parking is very tight. Further out there are stores with a few parking spots, until you get to the more modern big box stores surrounded by a sea of parking.

After I moved away I came back for a month and tried living without a car. I chose the very best rental location I could, about 13 minute walk to the center of town. While I managed, it required a lot of walking to get to the places I wanted to visit, "a tremendous toll on [my] time" as you say". Santa Fe does have a bus service, but running once per hour and only a few routes. I would not have lived without a car long-term.

I now live in Trollhättan, Sweden, population 60K. While people have lived here for a long time, it didn't become a city proper until a bit over 100 years ago. Sweden was a pretty poor country and it wasn't until the post-war era that people could afford cars. The modern city core was built before widespread car ownership. The apartment building I live in was built around 1960. It's literally on Main Street ("Storgatan" in Swedish). There are two grocery stores in the city center, plus a few others within a mile radius. Both kids (ages 4 and 6) walk to school, which are 3/4 mile away.

The city library, our medical center, the dentist, bank, and more are all within 1/2 mile. That option was not possible in Santa Fe. I had to do a 10 minute drive.

Sweden has become a wealthy country and many Swedes have a single family home with one or two cars. Trollhättan has a lot of suburbs which are not as central as where we live. But they do have frequent bus service with a good network. During peak time I think some of the lines run at 10 minute headways. The regular public busses are also used to carry kids to/from school - Sweden doesn't have dedicated school busses.

We also have big box stores, about 3 miles from where I live, surrounded by a sea of parking. And I can see how it's drawing stores away from the center of town. But unlike Santa Fe, in Trollhättan I can get on the bus (2 blocks away), get a direct bus to the complex, and be dropped off in the middle of the complex area. And those stores are mostly side-by-side and walkable, not separate islands in the sea. See https://www.google.com/maps/place/Överby/@58.313516,12.29464... .

We've lived here now for 10 years, without a car, and I think it's a decent efficient life.