Fiat money is not the problem, the financialization of economy is actually a common by-product of aging great monetary powers. The US chose to become a monetary power in 1945, rejecting Keynes' Bancor proposal.
Then in 1971, it found it couldn't keep it working, due to the very reasons Keynes explained to them at Bretton Woods. Arrighi argues this has happened 4 times already.
So Fiat money and the financialization of life is just an outcome of something else - that being a monetary superpower is just not sustainable.
Still, at the root, I blame the system itself, not specific participants.
People are far more willing to spend large amounts of other people's money on frivolous things than they would if it was their own money. Also, the ability for a government to create large amounts of money on demand allows them to spend on destructive activities which can create opportunities for certain connected people in the private sector. Price discovery in the markets cannot work if one party has a theoretically unlimited amount of currency. It just devalues the currency.
If the government knew that the budget was limited and they only had x amount of money to spend that year as an absolute maximum, they wouldn't be sending it to foreign countries as foreign aid.
Other powers have had monetary empires and they all go through this.
By using fiat, dollar as a reserve currency and the petrodollar, the US gets to export inflation and devalue everyone's currency against their own (I think). The best explanation I've seen of this are by Varoufakis, but there are others.
And replace it with what?