Gold simply does not back anything any more because it no longer correlates to the intangible knowledge that is valuable in an era where knowledge moves the economy.
Semi-/precious metals and stones (e.g., rose, white, and yellow gold and diamonds) are "standard
of [metallurgical and geological, respectively] beauty," and beautifulness is "intangible knowledge" (TPTB_need_war) (i.e., knowledge).
And a miniscule (and shriveling in terms of relative growth) portion of the intangible knowledge economy.
Relative size is an important concept in economics, as well as scalability and relative rates of growth.
And that 'beauty' attribute is not the attribute that historically imparted most of the value to gold. Rather gold was a more rare, compact, fungible, durable physical representation of physical value in a physical economy where trade of physical objects was the major aspect of the economy. It was like packing a bunch of land into a compact, transportable form. Whereas if you review my essay linked from the opening post of this thread, I argue that knowledge creation is accretive, spontaneous, and the property of the creator, thus it can't be tied to money or physical value. Knowledge creation is like an end-to-end principled network in that middle men (Theory of the Firm) can only obstruct it.