Looking back its not all that difficult, but at the time it is a lot of information to take on board. Air law lessons on a Friday afternoon when it's a beautiful day and you just want to go flying are pretty demoralising.
On the other hand, a lot of it is actually very interesting, even if a lot doesn't seem relevant to a real life airline job. As above, the people who moan the most either don't have enough passion, or just want a quick fix rather than learn the fundamental principles that will shape their future career.