What happens if the triple-pane low-e glass used in the home breaks, which eventually it will. Cavemen can't make that. What happens when the generator breaks down? If you heat with wood, what happens when your last chainsaw breaks. Are you prepared to cut with at two man saw?
"Off the grid" is an illusion of independence that may give comfort to some. But if civilization falls apart, that last chainsaw blade is going to be gone pretty fast.
I have some of the first Whole Earth catalogs, they were talking about “off the grid” back when facepaint and bellbottoms were popular, and people lived in domes.
Very few are willing or able to put up with the “off the grid” lifestyle.