Profit and loss accounting vs central planning

I think there's a lot of selection bias implicit in this premise. Most of the time constraints simply reduce the value of outcomes and we don't take notice because that's the normal state of the world.

One answer to your second question is that it's not obvious how to best handle complexity, but somehow we have to. Good system design seems to be largely about figuring out how much complexity users are ok with handling and not making them take on more than that, but balancing that with how much they're willing pay to have the complexity reduced.