It's kind of hard to find a "best university overall" because they're all so different. For example, Harvard medical school is among the best in the world, while MIT doesn't even have a medical school. At the same time, MIT's engineering is among the best in the world, while UChicago doesn't even have an engineering department. UChicago has some of the best graduate schools in business, law, and more in the US, but [insert literally any LAC here] has no graduate programs. And I can go on and on. While you could create a system that assigns different weights to each subject and then computes a ranking based on a university's average/total/whatever scores, that ranking would be near useless because an engineering student doesn't care about how great UChicago's econ is if they don't even have an engineering department, and an aspiring doctor doesn't care how good MIT's STEM is if they don't even have a medical school.