Well they need new content, and to make the game better. I also don't care for multiple passives and overloaded kits, but I can deal. Riot can't just sell skins, they need fresh character interactions. I've taken very long breaks from this game at least 3 times because I have no desire to get my rank past Silver and be a pro player like most others would.
Sadly I'm becoming a casual gamer, but I do consider myself skilled.
I like reworks when they make champions better. It's foolish to think that all old characters are just fine, when in reality a good half of them are dated. To me, Kayle is boring and often oppressive when she gets the right items. I don't care how good she may be with Devourer, I haven't picked her for two years. Morgana is okay at what she does, but I'm never excited when playing her. And fighting her? She pushes the wave and throws soil at your feet to make sure you can't get in lasthit range without suffering damage. Farm lanes are boring.
On the other hand, I think Amumu has a great kit and would only give him a visual update so his attacks have more pizzazz...I could also help his mana pool to bring him up to speed with newer champions who don't have that problem. Shen's ult and taunt are cool, but the rest of his kit don't fit a ninja, and aren't exciting. He doesn't need to be an assassin, but a fighter would look more appropriate. Just as they are doing with Urgot, perhaps giving Shen's ult to another champion would work if they replaced it.
I remember playing beginner bots at level 1 and being scared of Shen when he came around, but then I realized he hit no harder than a paper bag.