> Controlling and maintaining a complex system of feedback loops (that we still don't completely understand) is a very difficult task though, so I'm not surprised that currently the most crude methods (genocidal chemical warfare) are also the cheapest / most efficient.

Blanket chemical warfare is like feedback linearization. Wasteful in terms of energy and has other flaws associated with stability. There is a better approach, e.g., passivity based control, which requires understanding the underlying nonlinear dynamical system.

Interestingly this has been the same problem in medicine. However, there are more nuanced control-oriented medical techniques being developed (need better observers and actuating mechanisms).