Population decline is our chance to rebalance ourselves with nature.
I find the argument a little facile, because in that framework there is actually an even greater environmentally-destructive action... Deciding not to commit suicide.
Why is that suddenly important now? So it wasn't really about environmental impact, but about environmental impact implicitly modified by personal convenience and comfort? That's not what it sounded like.
> By committing suicide you only reduce your carbon footprint by however many years you have left to live. Not having a child however
With very few exceptions, a choice of dying today means someone will not beget any progeny on any subsequent day.
So no, unless you are suggesting some kind of death by snoo-snoo or tube-baby-farm scenario, shuffling off this mortal coil already encompasses the "no further children" choice and broadens the human-removing even further.
The hard thing to calculate is the net impact over time. But imagine someone in a poorer country that burns wood or coal, their electric sources are those too. They can increase their energy usage and actually improve their greenhouse gas impact.
There's no panacea but we can get there.
The economic efficiency and technological leaps that come with increasing the number of productive people would mitigate, slow, and potentially reverse climate change much more than surrendering the world to those who refine metals by mixing mercury over burning tires and will continue to reproduce without care for Malthusian handwringing.
Note how the US reduced carbon emissions despite an increasing fertile population and concurrent deregulation. While others who focused only on limiting their status quo increased emissions. Human society is dynamic, not static, and linear projections and limits do not play out so simply.