> reduce the impact on nature
Less bad is not the same as good. For example, electricity from solar panels is less bad than electricity from fossil fuels but there's considerable disruption to the natural world to produce them, not least of which involves mining for raw materials. In the same vein, we're nowhere near reducing pollution to safe levels or even reducing our overall pollution, all we've managed so far is a reduction in the rate of growth of fossil fuel use, it's still going up YoY.
while all true the population will shrink in less than a hundred years, consumption patterns are changing as economic surplus gets used to increase efficiency (from electric cars to simply having good insulation and a FIR camera to check, and so on), and hopefully land use patterns will also change (as lab-grown meat and other alternative proteins help to transition to a less cruel way to get meat, and that will require a lot less land to grow feed for animals)
sure, no guarantee that we cannot (and won't) fuck it up, but it's not hopeless