If I did nothing with it, it would naturally be grass, albeit extremely tall grass interspersed with thistles, burrs, and hemlock, which are far more negative than grass.
I don't spray it, remove anything from it, fertilize it, or use any ICE equipment to cut it, so that seems like a bit of a strawman.
And a lawn is extremely utilitarian. If you eliminate them, you eliminate a host of positive externalities: they're very aesthetically pleasing and good for mental health, they provide space to do activities, especially for kids, which promotes a healthy lifestyle, they're good for socializing, they're required for dogs, etc.
At least in America, we have no shortage of space. I don't know what people's problem is with people having a little recreational area.
I think this may be a bit high, my math may be wrong.
an acre of lentils for instance should yield about 5-8 quintals (say 500-800kg) of lentils a year. I imagine if you really care about that one acre, you may get higher yields still.
800kg of lentils would be about 2600 kcal/day for a year.
Rice would yield substantially more (but not everyone lives where rice paddies can thrive)
Corn: 1 acre yields 170 bushes / 5000kg, about 50,000 kcal/day.
Now, you need to eat other stuff as well to avoid malnutrition, but if you don't have meat, 1 acre seems to be more than enough per person. If you have to (zombie apocalypse, not because it would be convenient).
Caveat: IANAF, cannot provide any agricultural advice.
Lawns seem a good candidate. We take a piece of land that could provide most of the sustenance we need along with a host of positive externalities, then douse it in poison, expend enormous effort to remove natural fertilizers from it, pay to import industrially produced nitrogen to spread over it, and burn fossil fuels to cut it.
How a reasonable culture could view this practice as anything but stupidity or madness is anyone’s guess.