I notice that the thread title doesn't say "worthless", it says "useless".
"in" = "during"
Yes, gold would be "useless" "in" an economic apocalypse.
But not after an economic recovery.
UseFUL during a collapse would be things you need to survive until the recovery.
So, the advice would be, only buy the gold if you have "excess" wealth after you've acquired all the B's you need. (Beans bullets bandaids and batteries)
Even during a collapse things will be bartered. The means of currency may be work, sex, and yes gold and other precious things. There is always an economy, even in the darkest scenarios, there will be trade.