Why would you need a real-world application? We're all intuitive so abstract thinking shouldn't be too hard for most of the INFJ.
I guess that the problem is that high school math is pretty boring and does not show the real beauty hidden in mathematics formula/theorems. It's incredible how we can find mathematical/statistical laws that explain perfectly the laws of nature and some others who simulate real-world stuff really well. Also, there is a lot of creativity and imagination in mathematics, but that is something they don't show us in high school. Did you know that a mathemacian invented a full theory about multiple types of infinity? You can discover mathematical theories about everything, all you need is creativity.