I think a key component is that “suburb” has multiple meanings - and which one comes to mind when it’s mentioned depends on where you were raised/lived.

Some suburbs are the stereotypical miles and miles of identical homes with no sidewalks.

Others are actual older rural towns that have been consumed by the nearby metropolis - and these ones feel quite different.

There’s a kind of “suburb” that is usually quite lively - the rural suburb, often a pocket of relatively dense homes in a sea of wheat.

One of my indicators is lemonade stands. If they appear regularly, the area is alive.