I'm not sure innovation is really the issue, this article never actually goes into the alloys US Steel developed (of which there are many), and alloys are what makes steel steel really. It's always been fascinating to me how the just a tiny percent of another element in a metal can have an absolutely dramatic affect on the strength/resilience of the material.
And they tried more complicated alloys, for instance they developed Corten steel, the biggest example of which is probably the US Steel building in Pittsburgh, [1]. It's a steel where it's 'rust' essentially works as a protective layer.
More than anything this article shows US Steel simply couldn't compete with foreign suppliers. It's interesting to me that they don't even mention the Steel Workers Union, which was/is one of the largest and most powerful unions in the U.S. I'm not saying the cause, but if you need 5% more steel to cover the deficiencies in foreign steel in strength, but it's 20% cheaper, than it's simply cheaper to import more foreign steel.