I think the change to this situation is due to their kits. The difference between Kalista and Twitch is the way they're able to apply those stacks onto people. For Twitch, his ultimate essentially gives him a free Runaan's that pierces people and can hit targets from two times the distance than Kalista can. This, combined with the other steroids in his kit, make his E a powerful ability in itself when you're able to quite rapidly get all those stacks on a group of targets. Kalista has no real steroids in her kit like Twitch does, and she requires a Runaan's Hurricane in order to apply that same level of power.
Also, a few Rioters have actually labeled Kalista's release as one of the worst they've ever done since Vladimir. So I think some have recognized the mistake of giving her so much innate power in terms of mobility, utility, and damage.