The theory, at least in the British system, is that the domain experts are in the civil service. When you take over as Health Secretary, you have a senior civil servant who manages a department full of people who understand *precisely* how the NHS works. Your job is to define goals, they will tell you possible ways of achieving that and what the costs and expected outcomes will be.
Unfortunately, we end up with a political class that thinks they know better and when they’re told about the negative consequences of their proposed policies, they just ignore expert advice.
Personally, I would love to see criminal liability for MPs who vote for things that they have been advised will have negative consequences. If a policy is likely to result in a load of people dying, experts say this is the consequence, and you vote for it, that’s at least contributory manslaughter.