My basic ideas of quantitative models of economics are:

a) Even if you devised the perfect model, there isn't enough information to feed into the model to allow it to make predictions. I.e., too much of the relevant input to the model is unknown or unknowable.

b) Even if you had all the relevant input, the number of variables and their interactions mean you would need a computer (literally) the size of the moon to do the calcs.