Seems economists tend to ignore limits to growth, as if we live on a planet with endless resources. So little thought given to sustainability.

I don't think there are any actual, practicing economists who would contend that we live on a planet with endless resources. Quite the contrary - the idea of scarcity is fundamental to the core of economics. A huge part of economics is indeed the study of how scarce resources are allocated within a society.**

What many economists will say is that the amount of economic output that can be obtained from those finite resources can continue to increase, even as the resources do not. The rate of growth in economic goods is not limited by rate of growth of inputs, but can be increased by technology and/or efficiency in converting inputs to outputs.

That's why Malthus was wrong. That's why Ehrlich was wrong - or is wrong, since he's still alive and I assume his views haven't changed all that much.

Albaby


** For convenience, in certain contexts, economists may assume as a simplifying heuristic that the availability of certain specific resources (like sunshine or information in the public domain) are not scarce - but not resources writ large.