I define "lawn" as "whatever low-growing vegetation survives mowing and foot traffic." This includes probably at least a dozen types of grass, a few sedges in the prairie garden, two different plantains, several clovers, several violets, and of course dandelions. We don't fertilize, use broad herbicides, or do anything other than mow it. I spot-spray for noxious weeds like poison ivy.

As a result, even the "lawn" has a pretty decent ecosystem going. It has worms and other creepy-crawlers. It has insects on the flowers. The birds have grasped that the lawnmower does a bison's job, and after mowing they descend in flocks to pick through the short grass and clippings for exposed insects.

Go for it!

What makes a conventional lawn barren is that it's typically a monoculture of one or maybe a few grass types, cut short, and drowned in chemicals.

Used to be, grass seed always had one or more types of clover mixed in for fertilizer. But then companies discovered they could sell more stuff if they killed the clover with "weed killer."

When I'm patching bare spots, I mix clover seed with the grass seed, usually Dutch white. There are also tall pink clovers here, and occasionally tiny yellow ones. So they provide fertilizer, and I don't have to. Clover, violets, and dandelions provide pollen and nectar for insects, and the violets are host plants for certain butterfly larvae. So it's a small ecosystem, but a functional one.

Some parts of the yard don't get mowed much, and those have taller grass where critters can hide or nest. Fireflies like to sleep in taller grass, but fly over shorter grass in the evening.

Basically, the more diverse the plant life in your lawn, the more wildlife it will attract.