Meh. There's plenty of density for "a strip mall every four blocks". And you can make that structure totally walkable instead of requiring cars. The important thing is not to jack the rent through the roof.

Most suburbs don't, for no obvious reason. I did complain to the Mayor a few years ago that the grocery store four blocks from my house has only street access and no sidewalk access.

I'm not at all sure why the author seems to think that converted garages are great business incubators. That's a terrible idea. It's what my uncle did for his cabinetry business, but that's largely solo. I can't imagine wanting significant business traffic on residential streets.

If you mean zoning that requires first floor retail or whatever, sure. But mixed use zoning also means zoning that just doesn't ban small business, multi-family housing, and single-family housing coexisting on the same block.

The causality in your statement is backwards, because the lack of the latter kind of zoning is exactly what prevents inner suburbs from densifying organically. The current zoning in most of (at least US) suburbia is what artificially caps density.