All this is true. The US$ might be rubbish, and over the long term gold might be better. But imagine this scenario, which more or less represents my situation, and I guess that of many others: I have $300,000 mortgage and $100,000 cash (and perhaps $50,000 in gold). Say there is high inflation (above 7%) and the fed increases interest rates to 8-10% to control inflation. What do I do? I buy gold expecting hyperinflation, which likely will never occur, or I use all my cash to repay the mortgage, thereby saving 8-10% a year? Probably the latter. And will I also sell my gold to repay the mortgage? Probably yes.
Then I guess some people say that the Fed is manipulating the price of gold. No. They don't care about gold. They try to control inflation, not the price of gold. The conclusion is that gold is probably not such a good investment, even in relatively high rates of inflation, at least if you have a mortgage and not repaying it involves a direct, measurable loss.