Money is not infinite, at least for practical purposes, but it is socially constructed, and consequently not a hard constraint. If a nation has the means to obtain the necessary resources and labour, it will be able to build and run nuclear power plants.

This seems a bit naive. While money is a social construct it is also a proxy for resources. Also, to be clear, just because things are socially constructed doesn't mean they aren't useful. Most things are social constructs.

Money is a useful proxy when used to allocate resources to individual economic agents, but is not useful when analysing and coordinating an entire economy. In fact, the loss of fine-grained information and introduction of social subjectivity is often highly counter-productive.

I think I understand what you're saying? That money isn't a good proxy for issues of things like shared resources. A la tragedy of the commons types of issues? If that's what you're saying then I fully agree. Money has been a great tool for proxying local economic effects and facilitating trade but it is not nuanced enough to capture more long range phenomena like ToC. But I do feel like this is where governments are supposed to step in. While I'm pretty critical of authority I do see this aspect as part of the need for strong governments and limitations to pure democracies, as we have yet to find a structure where large swaths of the population can either be accurately informed or where we can have sufficient reliance upon experts. Obviously too much in the other direction (authoritarianism) comes with its own slew of problems (ones I think are worse).

(I do think a wide distribution of ideas that we can sample from, with a fairly normal-ish looking distribution, creates a powerful framework to build democracies. You do need anarchists, nationalists, and extremists, but not in large potions. When the mean shifts to any of these I think the system becomes unstable. But neither should we truncate the distribution.)

To briefly summarise my point, economic reality is determined by material factors, such as available physical resources and labour time, and money is a construct which controls access to those resources according to the society's power structures.