It is an argument. Life expectancy, infant mortality, access to food and housing, education and technology have never been higher. These are all good outcomes. Things are even getting better in developing countries on these measures. The only places where this is not happening is where superstition causes people to live under autocratic regimes that use imaginary sky people to control the population through fear and miseducation.

This is inescapable fact. Peoples lives in aggregate are getting better. That it is irritating to people pushing the opposite view is understandable, but doesn't invalidate the data. You can't just hand-wave it way and say 'doesn't matter'. You can't say it's not a valid argument because it 'might end' - which is in itself a poor argument.

It does matter. Life is getting better for a very large group of people, and that's good.

It's a fact. But it is not an argument. It is also not good if it leads to a major castrophy.

The concern is not that the good outcomes don't currently exist.

The concern is that the good outcomes are unsustainable because we are an increasing population consuming finite resources and generating serious new problems.

Do you have an argument that the current level of development is sustainable, or do you simply not know?