The amount of steel in use per capita in developed countries seems to have reached a constant level. About 69% of steel produced in the US is the same steel going round and round. If you ignore rebar, low-grade steel stuck inside concrete, it's even higher. It's the developing countries that are still making and using new steel. They don't have enough steel infrastructure yet.
"Mini-mill", in this context, means "smaller than a square mile". Here's Nucor's Crawfordsville plant.[1] It's not small. Compare with US Steel's Gary Works.[2] That century old plant is just about their last remaining big plant in the US.
US Steel somehow missed this change.
[1] https://earth.google.com/web/@39.97805108,-86.8271336,264.41...
[2] https://earth.google.com/web/@41.62932676,-87.36187513,174.7...