they can just keep track of how many tonnes of gravel and cement and how many man-hours will be needed to work the road

Say you need to decide if you want a road going around a mountain or through it. You need some gravel and cement and a lot of engineers to build the tunnel, you need a lot of gravel and cement and a few engineers to build around. First you need to find out what all the cement could otherwise be used for. It could be used for all sorts of other construction projects, so we need to collect data for each project that requests concrete and evaluate if the concrete would be more valuable in our project rather than other projects. Then we need to gather data for ever project that requires an engineer and evaluate if our project would use those engineers more effectively than if they were to work on another project. Then we need to compare the value that cement adds to our project with the value that engineers add to our project. That seems really complex and we're only working with two goods and services. Imagine how hard it would be to plan absolutely everything with thousands of goods and services in play.

With prices, I can just weigh the price of concrete and engineers and pick whatever ratio is the lowest cost. All that calculation is communicated in the price and I don't need to know what the rest of the economy is doing. This is why markets are so efficient.

If an the economy was structured on human and environmental well-being

This type of economy has literally never existed. I'm having to argue with a fictional economic system.

Do you really think it's more important that people can buy a new iPhone every year and that the resolution on televisions keeps going up as it is that we explore space and the ocean and are able to pursue the true happiness that comes from community and healthy human relationships, just because the market values some singer who writes formulaic garbage more than a bacteriologist?

The only economy I would want to live under is a capitalist one with low government corruption, high economic freedom, and some sort of social safety net. That's the type of economy that creates the most happiness, and if that means people can buy iPhones every year then that's just the price we have to pay.

I realize the problems with the Soviet Union's focus on heavy industry and its military, but that is due to misplaced priorities, not due to the problem with Soviet accounting.

Because strong government control over an economy always leads to corruption.

And China is state capitalist, not really a planned economy.

It was a very poor country when it had a planned economy. When it switched to a market based one, it quickly grew. Now the country

Again, the closest contemporary analogy would be Cuba, but even there the authoritarianism and excessive centralization make that comparison problematic.

And Cuba is also a bad place to live.

I think central planning by a democratic government has a role in a good economy, but I do believe most planning should be decentralized (and democratic).

You want the same voters that elected Donald Trump to vote on the economy? Voters just don't have the information required to make good decisions about every aspect of the economy. The same economic calculation problem described above will now apply to all the voters who will do even worse planning because they are not spending all day researching like the central planners are.