I don’t know if the statement you are replying to is correct “we don’t have enough steel” but what I can say is steel (well, iron) is about the most common material on earth. I’m surprised to see that aluminum is slightly more abundant, but they are similar.
https://en.m.wikipedia.org/wiki/Earth%27s_crust
However this chart shows that iron represents more than 94% of all metals mined. That is, iron (used to make steel) is the most commonly mined metal by far. So actually more common materials can’t be used as no more common metal exists.
Earth is almost entirely iron, but Aluminum floats in iron so it ends up being a large amount of the crust. But yeah, if we're ever like "gee we don't have enough iron" then we've far surpassed all other possible natural resource limits of the planet.