Modern money has operated as you describe for less than one human lifetime. It might not work long-term, and indeed there are significant reasons for worry that it won't. Not that it _can't_ in principle, but that it _won't_ due to mismanagement and misaligned political incentives. A future alternate system might well have deflationary characteristics.
If you mean Bretton Woods, that is in many ways an implementation detail. Ignoring the Great Depression (which probably _should_ be treated as a special case), and brief (~1 year) shocks after WW1 and 2, the last time the US, to take an example, saw _persistent_ deflation was the late 19th century.
But (b) money is given some real grounding by states; you can pay tax with it, in particular. It’s not much, and it’s not bulletproof, but by comparison to cryptocurrency, well, it’s _something_.
But really, it makes no sense as an argument that hoarding cryptocurrency is a good idea, because hoarding _money_ is, notoriously, a _bad_ idea.