In the patch recap for 5.17 Riot Jag claims that kalista is frustrating bcs of her support interplay
Sure, the ult is annoying... but that's not what's annoying about kalista. It's her passive - it takes away from her identity as a support-centric adc and is frustrating as fuck when you are playing a melee with no hard gap closer such as olaf darius garen mordekaiser etc etc