Living in a remote area can be as low-impact as you want it to be. The grandparent post said he was going off-grid so he should be energy self-sufficient. assume he'll grow some crops, hunt, fish and/or get locally produced/hunted/fished goods and you're left with whatever "luxury" he'll want to have which he can not take with him while moving out to the countryside. If you want to live the life of a city-dweller, getting commercial goods delivered at your doorstep at a moments' notice, yes, in that case you'll be doing everyone a favour by staying put in the city. Most people who plan on living off-grid in the boonies do not crave for that lifestyle, they tend to aim for self- or local-sufficiency as much as possible.
>he should be energy self-sufficient. assume he'll grow some crops, hunt, fish and/or get locally produced/hunted/fished goods
If you shared the farm and solar panels with a few friends you trust, is this close enough? Because you can have that in a city (search for Enercoop in France for the energy, and AMAP for _Association Pour une Agriculture Paysanne_).
Local, clean, self sufficient, etc. but with a minimum of solidarity. Also, you have a much smaller footprint by living in a city so it's a scalable model (i.e not one man for himself and après moi le déluge).
On a small scale this might work in a city but it is not feasible to build a city (as in a densely populated area, traditionally enclosed by walls but this is not a necessity, multi-story multi-tenant housing with the ground floor often used for business-related activities) where everyone lives like that. Agriculture takes space, this can be reduced by moving to vertical horticulture but that either requires artificial light sources or free exposure to sunlight - which is hard when those vertical growth beds have to compete for space with PV panels, wind generators, housing, business and infrastructure.
It might be possible to create a less densely populated city-like structure which works like this, the question is whether it is worth the effort. For those who see this as a fulfilment of some ideological drive it might, just like living off-grid in the middle of nowhere does for others. For the general population this is unlikely to be true though.
We won't be lacking space if we eat less meat (like our ancestor). We've only started eating so (too!) much meat quite recently and that's what taking all the space. Switching to mostly plant-based diet would resolve most issues.
>It might be possible to create a less densely populated city-like structure which works like this, the question is whether it is worth the effort.
No need to reduce density. Even big cities (like Paris) can procure most of its food from local farms. We just need to focus on local types of food (less exotic but not necessarily less diverse: for instance I get far more diverse vegetable from my farm than most Parisians).
Going vertical is unneeded and would require far more efforts than making farming more reasonable.
