Great topic Gary, it's an interesting can of worms to open
I've always tried to have as little an impact upon the planet as I can, a bit of an activist since my teens, and I suppose it's a philosophy and way of life, but I am also a realist, We, as humans have been interacting with nature since our time began, we've all made our mark one way or another, and that's reality.
I try not to make unesscessary journeys, I buy as little non recyclable or non reusable packaging as possible, natural fabrics when possible, etc; etc; I'm sure there are a few on here that are very similarly minded.
I also keep my outdoor kit in good condition and therefore I don't have to buy new stuff, I ty to buy once and have always choosen stuff that's hard waring and the best I could afford and I'm quite happy with second hand.
Not mentioned so far is that as individuals we should also consider the manufacturing waste and the subsequent transportation impact of anything we buy. It's interesting to see some of the kit advertised on this forum sometimes, 'brand new', 'bought two (or more) and don't need it' 'getting rid of some of my 75 bags'
Etc; you know what I'm getting at.
Personally and probably the same for quite a few of us on here, I think my trips out are pretty low impact, first choice for fuel would always be wood as it's the most sustainable and I don't think what little I use would have much of an impact to the biodiversity. I don't leave anything that shouldn't be there behind, even if it's other folks litter. The main environmental impact from most of us comes from any fuel burnt for travelling, car share if you can.
Indigenous peoples have shown us the right way, that life on this planet can be sustainable, they don't over fish or over hunt areas because they know the consequences of losing those natural resources. The modern consumer society doesn't seem to have learnt that lesson.
I think the 'line' can only be drawn by the individual, tread as lightly as you can through life.