i don't think you really understand the concept of representation
the concept of underrepresentation comes with the fact that there are many issues that women specifically face, minorities specifically face, the disabled specifically face, etc etc every demographic has their own set of specific problems they deal with, and our congress does not currently address the issues of these demographics, mostly in part due to not enough of congress being able to sympathize with these demographic specific issues to consider them critical enough to be put on the to-do list
or worse, when legislation gets passed that is literally against the interest of the demographic it is intended to help, because there aren't enough people in the position to address the issues that fully understand them