Need to fix the money before everything else can be fixed.
The issue is not double taxation per se, it is the inability to pay taxes at all. In order to pay the tax you incur by actually putting the gold/BTC/etc to use, you must liquidate some more of the thing to turn it into something the government will accept. That is what makes fiat real money, and everything else not.
The modern, technocratic government controls policy through many means, but monetary policy is a major one. The switch to fully fiat currency was an important transition point, and I do not believe it is a coincidence that wage gains divorced from productivity gains not long after the end of Bretton Woods. Businesses have always chased profit, but how they do it, what other interests if any they have, and on whose behalf they do it, have changed over time in accordance with (para-)governmental policy, including everything from "intended policy goals" to "unintended consequences" and "regulatory capture".
Though, the simpler point I was driving at about gold and BTC is just that when they are relegated to mere savings, they lose most of their potency. Assets are like potential energy to money's kinetic energy. However, the government accepting anything other than its own currency for payment of taxes would destabilize that currency. Only countries in dire straits would even consider such a policy. Hence, real money is what matters.