31 years of Batalah

Most yeshivas start teaching gemara in 5th or 6th grade and 'learn' for about 2 hours a day (in YSV i think it was from 9:00-11:00). There is also learning on Sundays, Fridays, and other half-days. If there are 180 days of gemara-learning in a year, in 3 years one learns about 1080 hours. A secular subject is only learned 40 minutes a day, 4 days a week, and about 120 days a year. So a year of one subject is 80 hours. That means 3 years of elementary-school gemara is really like 13.5 years of learning! After 13 years of learning you would think the kids should come out knowing how to read a gemara perfectly, but alas, this is not the case.
In 3 years of high-school there's at least another 1400 hours of learning-time (there's more hours per day and mishmar) which is the equivalent of 17.5 years of learning! So after 31 years you would think everyone should have completely mastered all gemara-related skills there are!
How come this isn't actually the case? I think it has to do with the emphasis placed on HLD (hours learned per day) instead of actual amount of learning skills gained. If there were only 40-minute periods but they actually emphasized learning the necessary skills instead of HLD, they could teach all the basic skills by the end of elementary school. They could give a Gemara final at the end of 8th grade which would test all the basic gemara skills a person needs. It could be a random gemara which everyone would have to learn during the test and then answer questions to show they understand it. This only sounds unrealistic because of the bad education system that's already in place.