The crit ADCs that were directly nerfed with the new crit items, and why they're bad.
DISCLAIMER: I DO NOT MEAN THE CRIT CHANGES WERE BAD. I'm just saying that some champions have been changed as a result of this patch. Overall, it was a buff.
TL;DR: Xayah, Kai'sa, and Jhin are in arguably WORSE places than they were before the patch.
Tristana, Caitlyn and Varus are experiencing shifts in playstyle.
I'm not providing solutions because I haven't analyzed/looked for ways to fix the problem yet, but I have analyzed the general situation of the ADCs that are experiencing bad performance.
Xayah is still garbo because they removed the crit on Essence reaver, so there's no point in building it to supplement her crit, but she's reliant on the mana regeneration. I'm still mad about how they gutted Xayah and left her to rot. Her utter reliance on teamfights and peeling leaves her at the bottom of the barrel, next to Varus. The prevalence of Sivir does NOT help AT ALL. She's forced to go Essense Reaver OR Infinity edge > Attack speed item > Whatever the one you didn't pick first, simply to remain relevant. Otherwise, you're either going to run out of mana or run out of damage.
Tristana is still garbo because her powerspike doesn't align with the new items, effectively making it a buff in some ways but a nerf in others. She builds Infinity Edge first, so she's even weaker before her second item, but afterwards she experiences that steady rise in power that still pales in comparison to Caitlyn, Vayne, etc.
Jhin isn't a traditional ADC. His crit chance was lowered, and he relied on Infinity Edge to maintain late game relevance against tankier bruisers. Now he doesn't stand a chance past 30 minutes. While he has bonus damage against squishies, he never had any trouble with them in the first place.
Caitlyn feels lackluster because of the decrease in early crit chance, when she used to be able to get 2 crit items before Infinity Edge. As of now, her powerspike if using 1 crit item and Infinity edge is the exact same as her chance was before 8.11, and her ability to run 2 crit items then infinity edge has been taken away. As a result, she has to actually rush Infinity Edge first, which removes her attack speed headshot stacking power, and dramatically reduces her trading effectiveness, but enables her to have stronger Q's, R's, and W/E autos.
Kai'sa is in the same boat as Caitlyn, but even worse, because of the 100 AD and 100% AS requirement forcing her to go Infinity Edge first THEN Rageblade THEN the FIRST attack speed crit item. Good thing her kit provides her with plenty of AS steroid, poke, and dueling power because if it wasn't overloaded she'd be way worse than Xayah. No, I'm not kidding, Kai'sa is extremely reliant on ALL aspects of her kit to remain afloat now.
Varus will never be good unless rageblade is good or lethality is good, so I don't consider him an actual crit ADC, much like Jhin. With the crit changes however, he has two lackluster options now. Go tacky on-hit, or go tacky crit ADC.
In general most ADCs experienced an uptick in viability, but there are some that were forced to adapt due to the reduction of crit chance.