“So, government should just stop trying; cut taxes and get out of the way.”
A handfull of technocrats in the government operate on the mistaken belief that they can make better decisions than that which is reflected in the collective wisdom of the judgements of hundreds of millions of people.
Bears repeating.
You are absolutely correct. In the 19th and early 20th it was possible for honorable and intelligent people to deceive themselves into believing they could "manage" the economy and make the world a better place.
The economy has since become orders of magnitude more complex and faster moving. Only a fool, an aspiring tyrant or someone intentionally deceiving himself could believe the same today.
It's like controlling the weather (or the climate). It's not just that we'd likely screw it up, it's that we don't have a clue how to go about doing it. If we would admit to ourselves that we don't have a clue, we just might possibly find one. Since we won't, we won't.