Sustainability is almost always subject to circumstances and context in a practical sense. Many people who decry "unsustainable" practices seem to forge this despite all the lessons of history.

250 years ago, it would have been completely unfathomable to imagine feeding 8 billion people with the technologies of the time. I'm not just talking about it being unsustainable but temporarily doable, it would have simply not happened without maybe two thirds of the world rapidly dying of hunger. Yet, here we are today, with the lowest relative proportion of the world in recorded history in danger of famine.

This of course slowly isn't sustainable WITH present technologies being widely used. If those technologies change however, it could indeed become sustainable, just like what we have now is far beyond the capacities of previous centuries. Instead of default leaps to new prohibitions in environmental and climate change discussions, more focus should be made on promoting new developments that let us both live well and in large numbers while harming the world less.