I have learned that grids are one of the most important things, especially if you want to be precise when arranging your designs and type in a specific way. I have also found out that there are many different types of fonts and classifications of type. Each one can give a different feeling than the other.
Even though I never thought any of the stuff I learned was entirely useless to me, but there was only one thing that didn't seem as important to me as everything else I learned. I don't think of the phrase "Typography is what language looks like" as a very important thing that I had learned. As to why I feel this way is probably just because I never really thought about it. It just seemed kind of like common sense to me like walking and talking.