Before people started using this keystone, she was in a bad place. Sub 50% winrates in every role, easy to beat with literally any laner. I said it before and I'll say it again: Soraka could beat Kayle in lane. That is before Kayle started taking Kleptomancy.
This keystone has been nothing but problematic for the game due to the way it behaves and how it counts a spellcast. They fixed this for Ezreal because he was abusing it so badly, except in his case he could also farm.
I heard from someone on these Boards that Riot planned on nerfing Kayle Jungle if they saw her playing that role too much, because it was to circumvent her weak early game by placing her in a role that could minimize encounters with other champs. Well, people are definitely circumventing her weaknesses again by giving her an early source of gold from Kleptomancy. In lane she's supposed to struggle to cs and reach her item powerspikes, but now she can easily get to them by just poking people and sitting under tower in a safe zone because you can't dive her without 3-4 people hard engaging, and even then it'd be hard to get everyone out alive at that point.
Give Kayle the Ezreal-Klepto treatment; make her e not count as a spell cast until the ranged auto lands, then give her the opportunity to hit someone for gold.
I think after this people will go back to either not playing her or dedicating time to learning how to play her, and when those people figure it out they'll post guides and videos about how to do things and her playrate will go back up to a nominal rate. I have personally dedicated my time to learning how to jungle with her, but that's kinda hard now that she's almost permabanned because she has a bad reputation in top lane.