Ok so GPT-3 can model biases well. This still doesn't solve problems such as the optimal aggregation of citizens' preferences, which is the actual optimization problem of policy making. Just to give an idea of how complex a field this is, there is a subdomain of economic theory and information theory called social choice https://en.wikipedia.org/wiki/Social_choice_theory that works with these issues and itself does not have many theories about policy formation, mostly choice between already formed policies. If a neural net finds the way to write policies that are Nash equilibrium collective decisions in all possible democracy systems then we will be close to solving the problem.