Depends on what's causing decline. If its people not wanting kids then it's a good thing, it it's people not able to have the kids they want because Capitalism is squeezing them dry or assholes like Musk is reducing work flexibility then it's a bad thing
No, better and more effective and efficient systems help with Climate Change like Nuclear and Renewables, banning plastic in favor of infinitely recyclable glass, or more relevant, let people work from home instead of driving to an office building.
We live in a world of fixed costs that looks like it’s variable