The lump-of-labor thing was called a fallacy by someone arguing that the amount of labor to be done in society is not fixed: if you happen to have people with a

The lump-of-labor thing was called a fallacy by someone arguing that the amount of labor to be done in society is not fixed: if you happen to have people with a bunch of time on their hands, they can usually find something useful to do that would not otherwise get done. And as for the rational actor model, everyone knows that it's not true; the reason people use it is that its predictions are often surprisingly close to the truth. ("All models are wrong, but some are useful.")