And it is really like that.
I asked in the German ultralight forum, who is replacing camping equipment with bushcraft skills.
They answered me, it would be impossible to cook over open fire, because it would destroy the nature and you would never be sure, if you are able to light it, because it could rain, and it would take to long to use some sticks as pegs and they wouldn't find trees in Europe to attach a tarp, the sparks would always jump out of the fire to destroy the tarp or set the equipment in fire etc. Nobody was using bushcraft techniques.
That means: The ultra light community is hiking with rucksack weights of 4,5 to 5 kilogramm, some with 2,5 kilograms, (all together, but without water, food and fuel), carrying a lot of ultra light nonsens around!
If we use the materials they are using, and take things which they carry around simply out of the nature, we easily should be able to hike in summer times in woodland with equipment of 1 kilogramm I guess.
A Poncho of 300g, a sleeping bag of 400 g, a plastic bottle of 30g, a titanium mug of 100 g, an opinel knife of 40g, a bic mini lighter, a petzl e-lite torch of 25g etc. That's nearly nothing, but works very well!
That equipment you easily can carry in a Smog and field trousers! You can leave the rucksack at home.