No, the real issue is that under the "gold standard", the money supply is related to gold finds - which are random events. It's not like the supply of gold is actually fixed. So someone could find a huge gold vein tomorrow, and crash the world economy. Just like printing money, but done by individuals!
Also, there is simply the unavoidable result of a fixed currency:
Country X says "my dollars are worth exactly 1 Y", for any option of Y. You take your money, and short lots of X dollars. Then you counterfeit X's currency (or wait for someone else to counterfeit it). Now your "short" position is worth more than you paid for it. Country X's only hope is to deflate their currency voluntarily each year, to account for counterfeiting.
This happened to the US several times, and that is why we are now off the gold standard. It's amazing how few people bother to figure that out before advocating the gold standard!