> But let's be fair, "induced demand" is just another way of saying "insufficient supply" because otherwise massive roads in the middle of nowhere would instantly fill with cars.

No, "induced demand" is a variation on "if you build it, they will come".

e.g. Traffic is heavy to the new suburb, so you add lanes. But now people are willing to expand the new suburb, or to build houses even farther out because of the new highway. So you need to add even more lanes ...