It's a couple of different things that make Wrath better. For one it's not just standing in the same place for long periods of time like a lot of the KF encounters. Pretty much all of KF, you just went to the same two positions. Wrath has you all over the place. KF (specifically the Oryx fight) relied extremely heavily on mechanics, so no matter how high your gear was, you were still extremely prone to a wipe. The Oryx fight was also going to be the same length no matter what you do, whereas all other encounters can be determined by your gear. KF also just had a lot of waiting around. Waiting on the ships to take you places, waiting on other players to finish the long jumping puzzles that reset you a long way if you make a mistake, waiting for Oryx to regain the favor of the darkness; it just got tiresome. Really the only times that you're waiting in Wrath is if someone is falling behind on a jumping puzzle, but the puzzles are short enough that it isn't bad unless they have no thumbs.