The earth's natural carrying capacity using 19th century technology is a question of great debate. The best guess is around 2 billion, about 1/4 of where we are now.

That is not an empty world by any stretch of the imagination. If we got to 2300 with a population of 2 billion and civilizational continuity being preserved, I would regard that as a "win".

A big part of making that happen is avoiding big spikes in the population dieback. Shrinking your population 50% over 50 years at a rate of 1% per year is infinitely preferable to shrinking it 50% in one devastating year.

Managed retreat is so much better than uncontrolled collapse.