Well, compare the global statistics for population and economic activity for the relevant interval, and project that forward (with some adjustments for counter-trends like the business cycle, probably).

In 2000, the global population was just over 6bn. And in 2020, the best estimate is that it's around 7.75bn.

In 2040, it seeems reasonable to guess that the global population will be about 9bn.

You can do the same thing for economic activity. On the global level, it looks like growth will be the rule for several decades yet.

If you're seeking evidence for declines: It looks like the global population outside Africa might peak sometime in the 21st century. That probably won't be for climate reasons, of course. You could argue that it's for sustainability reasons.

Some people also believe that long-term economic growth is converging with the (declining) rate of population growth. That's an intriguing theory which is worth analyzing some more.

But all significant evidence suggests that the story of human civilization in the 21st century will continue to be one of growth and general abundance. Despite the persistence of some difficult struggles, like combating poverty and political instability.