So if I understand you correctly, if I wanted to switch from a non-optimizing policy to an optimizing policy, I'd have to choose whether to switch to a policy that's Pareto-optimal with respect to my current beliefs, or to a policy that's Pareto-optimal with respect to old beliefs. And if we don't know which beliefs to use, we can hardly say that we "should" choose one or the other.

Is that statement close to your point of view?