Theoretically speaking, not all water use is renewable like rainfall, you can in fact deplete aquifers, and ancient near east in fact desertified due to unsustainable water use. Ditto for land use, you can in fact erode and degrade topsoil, ancient near east etc.

Skimming the report, it doesn't do reasonable job of taking land use and water use into account, but in principle, there's nothing wrong with taking unsustainable portion of land use and water use into account.

Freshwater and fertile topsoil are easily exhaustible resources. There are rivers (e.g. Colorado River) that are drying up due to overuse, and much of human waste gets either polluted with chemicals or ends up flushed into the ocean, never to be reclaimed. Once you dry up one river too many, you'll have both starvation and depopulation, but also daily shellings.

New rivers can also form, and volcanoes create new fertile land.

How much does the Mississippi spill into the ocean and why don't you consider that a massive waste of freshwater?

Are humans patient enough to wait for the next volcanoe?

I like people, and eating meat, and lots of other things...but I and just about all of us are burning through the infrastructure that makes humans possible. And when humans aren't possible, there won't be any more humans. That's reality.

The physical systems on which we depend for survival do not care about what we want. Our only hope for maintaining a human population is to recognize that.