Why slow reaction alone does not excuse the Dantons

Were the Dantons merely victims of a procurement system too slow to react to HMS Dreadnought?

Only partly; they were ordered after Dreadnought was already operating, so the failure to change course was itself significant.

French procurement did change slowly, but the Dantons were ordered after Dreadnought already existed and was operating. That timing weakens the idea that France was trapped only by an irrevocable earlier commitment. The failure to change course involved decision-making as well as administrative pace.