I don't get your jump there - we don't need to be able to forecast weather to be able to build a roof to shield ourself from rain. The same way, even if economists have no ability to forecast the market, we may still be able to devise social rules to soften the negative consequences of a market crash. Or we may not, but it's a different issue.
I also don't get what you call "normal workings" of the economy. Even most of the libertarian I know about still want to enforce and protect private property, using external force to do so. So they are already distorting the "normal working". If you want to use public force to ban stealing, then you're already thinking you can improve on the "normal workings" of the economy.
You certainly do need to be able to forecast weather to justify building a roof to shield yourself from rain! As opposed to blizzards, the monsoon season, sand storms, or any of the infinite varieties of weather which do or do not exist in your particular location.
I also don't get what you call "normal workings" of the economy.
The normal workings are set by long tradition and experience and local experiments (see the Austrians like Hayek), which is data-driven stuff completely opposed to the top-down economic interventions I contrasted with.
Here's the new thread for posting quotes, with the usual rules: