https://www.paulnathan.biz/commentaries/27-the-death-of-bretton-woods.html

Fixed exchange rates, flexible rules…. Under the rules established by the Bretton Woods agreement, the gold values of a member nation's currency could be altered "as conditions warranted." This distinguishing feature of the Bretton Woods system exposed a drastic ideological departure from the gold standard.

Under the gold standard, no natural conditions would ever warrant a change in the gold value of a nation's currency. Under a pure gold standard, all the money in circulation would be either gold or claims to gold. Any paper money would be fully convertible into gold. There would be no difference between claims to gold and gold itself, since, if claims to gold circulated as money, the gold could not.

Bretton Woods was established with the intention of aiding governments in exercising their powers of inflationary finance. Government leaders knew that the gold standard prevented them from fully pursuing domestic goals that depended on deficit spending and prolonged, artificially induced "booms." They detested the gold standard for its fixed rules which brought adverse economic repercussions whenever they refused to adhere to them, and they detested flexible exchange rates that exposed the government's policy of currency depreciation.

The political temptations of artificially increasing the money supply in order to "stimulate the economy" prevailed against the gold standard and brought the beginning of a "new era": fixed exchange rates with flexible rules, the exact opposite of the gold standard.

No longer would politicians adhere to the discipline of the gold standard. No longer would they have to restrict their deficits or domestic money supplies. Government leaders would make their own rules and fix the nominal value of money by decree. And if "conditions warranted" a reduction in the nominal value of a nation's money, it was agreed that a nation could devalue up to 10 per cent after the formality of obtaining other nations' permission. This was called the "adjustable peg" system.

The great ideological distinction between the gold standard and the Bretton Woods system, then, is that the Bretton Woods system was ostensibly intended to stabilize exchange rates, but at the same time it anticipated that governments would not defend the value of their currencies. Worse, Bretton Woods institutionalized a method which allowed and condoned future currency depreciation.