I used to be forced to play a game of cat and mouse (me being the mouse) in the early jungle when playing tank junglers. Constantly being on edge and constantly predicting the enemy jungler's moves.
Right now people have forgotten how to deal with tank junglers early. I can walk around with 50% hp and not be punished for it. My thought process is still "crap I'm a goner if enemy jungle shows up when I try to do the next camp." but they never do.
People have devolved into either cheesing early or aimlessly running into the jungle without forethought of where exactly the jungler might be in what kind of condition. Back in the days (s1/2) people had certain timers in their head for each possible jungle route and tried to predict which route the enemy had chosen and decided to invade when the jungler would be at his weakest in a certain route. That and avoiding that was one of the biggest make or break jungle skill factors. There were others important ones as well but that seemed the most important. You also saw people play a lot of different jungle styles which are lacking right now partly because of how riot set the entire system of jungling up.