Surely it is not that economists are stupid. Most of them are seriously trying to probe the depths of the intricate web that is our industrial society. Let's look at a few of the underlying difficulties. But the ultimate result is the reductio ad absurdum. Our specialization has given us lots of pieces but no overall pattern into which to fit the pieces together.
Nature is pure mechanism and has no function except to be exploited.
Material progress is all that matters. Quantity of things is more important than quality of life. Efficiency is the prime virtue. Atomistic individuals are the base of civilization, and social community is an aberration. All persons are rational, and rationality is defined in terms of single-minded pursuit of wealth.