Jungle in current state

Okay so i am not here to complain that's the first thing, i just want people to help me understand/learn specific riot decisions. So i've been maining jungle for some time and i've noticed couple of things, one of them, how variety of champions is limited there. I am platinum 2 right now so it may be different in higher elos, but i think it is sad cause all i see among platinum junglers are Kayn, Lee, Amumu, Sejuani, Reksai and thats about it. Dont get me wrong im not saying that other junglers like rammus, skarner, rengar are useless, they can do something but they are not picked often, cause why the hell would you? You can pick the most broken champions in this patch cause thats how you win the games? So let me get this straight, even if you want to have fun with this game you have to play the champions that are the most broken at the current patch? So its like having fun, but at the same time you can't play with your beloved champions cause they would be destroyed by the others. From all champions i've mentioned, the only champion in my opinion that has reasonable damage is lee sin, but the others are just out of this world, like have you seen reksai's early game? he literally destroys everyone who stands in its way. Then we come to kayn (i main him atm), i love this champion, but even i can see its stupidly broken and im not speaking about its damage, im speaking about its mobility (blue kayn, red kayn is a whole another story), not only kayn can one shot people, but he can aswell be everywhere in the map, you literally travel from botlane to toplane in what? 15 seconds? Thats exactly how everyone gets fed while playing with kayn, cause they can be everywhere, it doesnt matter if you make a bad decision i.e taking red instead of helping botlane when they are getting ganked, cause you will be there in 5 seconds and last hit all of them. And then we have champions like kha zix who for some reason was nerfed like what? 5 times? Instead of nerfing duskblade riot decided to completely ruin the champion then gave kha zix unlimited ultimates then took it away and here we are, he has LITERALLY no impact in teamfights anymore unless you give him 20 kills in first 20 minutes, cause lets be honest the current "meta" champions destroy all of these outdated champions. And wait a minute it gets better, cause we have a champion like wukong, yay! Did u try playing with this champion, this guy used to deal damage, but suddenly without any drastical changes he became completely useless, like it doesnt fit into my head HOW? Thats why im asking you to help me to understand, why riot thinks its okay, when champion dominates league for 2 months straight and doesnt do anything about it? And in the end how in the world champion like wukong, without any superior nerfs, ends up being the weakest jungler.