You used fire as your example. A hot topic.
So, lets talk about shelter. No, I wouldn't cut trees and boughs to make a lean-to, in order to cut pack weight. I will use trees to hang my hammock, taking care not to damage the tree, which really doesn't require a lot of care. By default, if stuck sleeping on the ground, my pad/ground cover footprint is smaller than any tent. Food...I never 'forage' to save food pack weight...but I will pick a berry once in a while.

I like to leave campsites as though I was never there...and regardless of whether you are going lightweight or not, I find that many users don't typically care or know how to care.