But, right now, she has insane damage and her arrow, which most other ADCs can't keep up with. With Ashe and Jhin as the top tier, if you see one, you're forced to pick the other just so you can keep up in damage. If one is banned and one is picked, bot lane is almost guaranteed to lose. Yes, they die when jumped on, but they have enough poke to make sure that you can't jump on them. And them just existing with the amount of damage that they have right now makes literally every other ADC unviable when compared to them. Honestly, I'm glad that they got nerfs this patch. Not sure if it'll be enough because I haven't seen either of them yet, though.
Let's look at Twitch as an example. He's strong and has decent burst in his kit with his E, but Ashe and Jhin have so much range on him that they just destroy him. For Ashe, it's a skill matchup between both players in bot lane. If your bot laners are just outright better at their picks than the enemy bot laners, they can win. However, the instant Ashe hits 6, if Twitch hasn't killed her several times by that point, she just fires an arrow into his face and kills him. And then does it again. And then again. Every single ADC in the game, when playing against an Ashe, has to crush her into the dust to the point where she's useless other than the arrow in order to not just have the lane turn into her favor the instant she hits 6, and even then they still have to play 100% perfectly to avoid throwing. The arrow moves fast enough that you can't dodge it from a short distance without instant mobility, so unless you're playing Sivir, Nocturne, have your flash up, or have a QSS, no matter how far ahead you are, Ashe can just ult you and kill you. Even point-blank, it's a 1.5 second stun. If she has her Q stacked up beforehand, you'll be lucky to survive that if you aren't a tank.
And, she's the only ADC I can think of off the top of my head that has a stun or something else that prevents you from moving and attacking entirely. And don't say Urgot because he's so off-meta and obscure that nobody will be playing him in ranked, plus he also immobilizes and stops himself from attacking during the duration.