Due to monetary policy that the Government have, they are freely to print and devalue fiat easily, even though we want to takeover and take care of this thing, we can't messed up with the Government in this kind of matter cause you know guys what will happen, we could end up in bars. Inflation is a disaster of fiat currency since the very first time, when things got their value and people started to trades commercial products.
Technically, fiat is not that useless, it is that the Government makes it looks and really useless because of their power creating more of it, Governments are worthless, in my jurisdiction.
You cannot say that the government is worthless. Why do I say it that way because there is the main principle of the function of government that is maintaining public order and security so that every member of society can feel happiness. In maintaining order, the choices made are the best choices from bad choices. In the current era of globalization, domestic stability is also influenced by other countries' external policies.
The problem of the fall in fiat value is not only caused by the government's policy to print new money and not all governments adopt a policy of printing new money to overcome the economic problems in their country. Printing as much money as possible is allowed as long as the printing of money is backed up by gold, so the problem is there is no backup (creating out without nothing). Every fiat money printed by the central bank will become a burden (debt) to the economy.
In addition, why FIAT money becomes worthless because, since the collapse of the Breton Woods system, the world's monetary system automatically relies on the US dollar, as a consequence many countries in the world keep their foreign exchange reserves in dollars. International transactions such as import-export, oil trade, and financial services use the US Dollar as a transaction tool. So, indirectly there is a high enough relation of all these countries to the stability of the dollar. So the instability of the dollar will cause inflation to export throughout the world and the burden on the American economy will be felt by the entire world community.