More resources per person should lead to higher GDP per capita and a higher standard of living as population declines

More resources per person should lead to higher GDP per capita and a higher standard of living as population declines. 

Most models of economic growth seem to be based in part on population growth. A decline in population can be seen as a negative or positive, although the word "decline" isn't inherently positive. 

Malthusian thinking is wide spread. Here is an example: https://www.overpopulationawareness.org/en/

"Our planet can offer a quality of life comparable to that enjoyed in the European Union to no more than 2 billion people. With a population of 8 to 10 billion, welfare per person on a world scale will drop to that of a poor farmer who can scarcely provide sufficient food for himself and knows nothing of welfare. And thus we will have to share everything fairly in order to avoid disputes or war.

The climate is changing – and it matters little whether this can be blamed on human activity or on changes in the solar system. The sea level only has to rise slightly in order to cause a great deal of valuable agricultural land to disappear. At present we seem to think that we can keep ahead of famine with the use of artificial fertilisers, by the inhumane breeding of animals and other survival strategies.

Human beings have a tendency to want more and more welfare. World-wide the numbers of cars and refrigerators are increasing before our very eyes. But there will come a time when population growth and welfare collide."

If you invert that thinking a consider countries where the population is declining like Japan, Italy, Taiwan, they should be looking at a brighter more plentiful long-term future?