I don't disagree with you at all. In fact, in a number of my posts I have argued that our decline/demise/collapse due to Tainter's diminishing returns process is exacerbated by ecological overshoot and the damage that has been wrought on our planet because of this. The symptom predicaments of overshoot include: resource decline, environmental degradation, biodiversity loss, sink overloading, etc., etc., so you are bang on that there is no where left to move to and start all over again as many do in the face of collapse.