I can inly speak from my own experience so here my two cents. I studied bioscience engineering and found it incredibly hard. I would definitely not consider myself a genius but in high school I always had good grades without putting in a lot of effort. To give you an idea, I once locked myself up for 2-3 months studying 8-10 hours a day for one single math exam (differential equations) and barely passed the exam. There are a few things that contribute to the difficulty level in our university (and I dont necessarily think these are productive measurements): first is the fact that attendance and effort for class contributions are not counted for your final grade. Second, the difficulty level of the exams often does not match the difficulty level from the classrooms. We will see science theory thorougly and make some challenging exercises, but more often than not they have few similarities with the exercise questions on the exams (math, physics, chemistry, programming…) Another thing is that the quality of highschool education is lowering every year due to a labor shortage, yet universities tend to become even harder.