The models are mostly easy to understand (from simple differential equations for the simplest models to agent-based monte carlos modeling everyone ina region),

The models are mostly easy to understand (from simple differential equations for the simplest models to agent-based monte carlos modeling everyone ina region), but the parameters in the models depend on people's behavior, which is not something that can easily be predicted. Argonne National Lab has simulations where they simulate every person Chicago and where they might go and who they might run into, which, given the correct set of behaviors would probably work very well. But... how do you predict how people will act in a week? That will depend on the weather, court decisions, number of deaths in random countries, how rousing a speech a politician might give, etc. If we could control how people acted, I bet the models would work very well.