I don't really have a problem with getting enough steel made. I have a problem with completely unrealistic ferrous metalworking. You need as much flux as you do ore. This is not how it works in the real world. The in-game recipes are completely silly. Flux is mainly used for removing carbon, coke is used to add it, yet you need both, for both steps? Nope. That is not how ferrous metalworking works. Before the reverbatory furnace, the fuel used in smelting iron would introduce too much carbon, yielding pig iron as the direct product of the first step. Another step is required to make usable, non brittle wrought iron. If just the right amount of carbon could be removed in this step, steel could be made in small batches. More commonly, carbon was added back into wrought iron in a third step. The amount of flux used was minimal in comparison to the amount of ore used.
Dwarf Fortress technology is high middle ages tech, in general. At that time in the Western world, the most common process was the bloomery for producing sponge or pig iron. This was refined in a finery forge by heating and hammering to squeeze out the inclusions, producing wrought iron, or careful management of the process would result in removing the correct amount of carbon to produce steel. Outside of China, no better way of making steel was known at the time. The puddling furnace and the cementation process weren't introduced into Europe until the 1500s.