A society that spends all its time and effort on bad investments like building statues and blowing them up again, is a society with a problem, yet by the metrics used by conventional economics, it'd be doing great! Full employment! Tons of production! GDP increasing!
As long as economic activity is driven by individuals it is inherently better.
My build-statues-and-blow-it-up example was deliberately exaggerated for clarity and effect. In the real world malinvestment tends to look like asset bubbles, the construction of houses that nobody needs, "airports to nowhere" (like the cases of that happening in Spain) and so on. It may look like beneficial economic activity when you're zoomed all the way in, but when the free money dries up, suddenly it becomes clear that maybe strippers shouldn't be allocated two houses, or maybe airports should be built near population centers, and so on.
Anyone who can print money from nothing can essentially override the judgement of wider society about how best to allocate resources. Note that resources can also be allocated towards savings, but that tends to suppress economic activity, so people whose job performance is judged by measuring economic activity invariably end up attacking savings. Hence the frequency with which central banks try to push down interest rates.
Of course at that point people are actually treating the entertainment value as an asset rather than the statue and explosives themselves so maybe that’s also completely reasonable.
> That probably means it's a good idea ;)
This is a really bad heuristic.
Going "full reserve" would drastically contract the money supply and have pretty severe effects on the real economy.