Or do you really think that if the Roman gold coin had been heavily debased through ages, the European Medieval and post-Medieval rulers wasn't doing essentially the same? I guess they were doing just that, though on a much larger scale than any Roman emperor could ever dream of. In fact, financing wars through inflation (or debasing currency as in the case of the gold coinage) is a viable economic means after all, if not downright inevitable (which history repeatedly shows). Really, if a nation wages a war against another nation (or one city against another) and ultimately wins the war, all expenses are covered by looting the other nation. But if it loses it just gets looted itself (such is life)
Assuming what you're trying to say is "if we are talking about real world examples, wherever and whenever gold (or silver, for that matter) had been used as base money, it didn't end well":
China is a counter-example (i.e. in addition to Renaissance city states.) China had gone through the entire Western debacle with state issued money by the 15th or 16th century (inflation, financial repression, etc. over the previous few centuries) that it decided to use physical silver for money sometime during the Ming dynasty. I guess it must have been so disillusioned with state issuance that the silver wasn't even coined. Ingots were weighed and cut on the street. The system functioned for centuries until the British Empire naturally saw it as a threat to its world system. The problem of China was not being able to resist the British militarily in the 1840s.
The problem is not gold and silver per se, but the state's propping up of its own issued money or debt, whether fiat, 'backed by' gold/silver, or physically embedded gold and silver.
When you have a money that the state cannot (or realizes it shouldn't) manipulate, you're (literally) golden. Part of the problem is allowing the state to define the monetary unit. Once transactions are denominated in the state-defined unit (dollar, franc, etc.) the system is open to such manipulation, although state-defined units are harder to prop up in multipolar worlds like Medieval Europe than in, say, pre-15th century China.