Actually in the DS9 episode Penumbra it was stated that the Galamites were supplying the Federation with Duranium. It would seem the war was so bad that the Federation had to rely on allies to provide them with raw materials.
Doesn't that strike you as poor writing?
To rely on any 1 species or source for something as vital as ship construction materials in the face of highly advanced technology that is basically integrated EVERYWHERE and is capable of creating practically anything is utterly unsustainable.
Ship construction materials would have to be made from readily available superior synthetic materials that can be made in abundance using the least amount of energy and resources... especially if we are talking about sustainability (let alone a war which was EXPECTED even).
I find it highly improbable, that they were never able to analyze the material and make a synthetic version - plus the material is NOT new.
Besides... Voyager constructed the second Delta Flyer which had a Duranium enforced hull (the first version had a Tetraburnium alloy that allowed the ship to withstand heavy atmoshperic pressure).
If Voyager was able to construct that ship at a spur of a thought and synthesize these materials (which they had to), the raw materials needed would have to be readily available in their environment (almost any given environment) that can be turned into synthetic Duranium, or Duranium is already replicable from energy alone (although granted, Voyager also could have traded with other races to get Duranium... if not the raw materials needed for its making).