Take a very simple example. Labour is the only input, there's a constant returns technology, and labour produces one apple per hour.
Start at full employment, where everyone works 40 hours per week, and nobody wants to work any more than 40 hours. ...The first thing I notice about such simple models is that in such a world, people would have no need of "simple models" to help them understand what is going on. In short, the "simple model" thought experiment has no cognitive dimension.
(Unless it's an economist trying to sound like a physicist)