wtf happened to Kalista

A whole bunch of nerfs happened that's what.

Her passive

She needs spot on mechanics and a team that's built around her. You won't find one below diamond and you won't find the other outside of the LCS who can pick better champs.

she lost tier 3 boots.

bork nerfs

burst/youmuu's is insanely popular and she cant build it and loses to anyone who does build it.

shes just too weak the first 20minutes of the game. but if they do buff her at all she becomes a late game monster again.

when tanky/immobile targets become popular again so will kalista, until then, shes kinda trash for a team.

She's just undertuned and has a high skillcap. Her playrate is significantly low and any kind of buffs done to her usually ends up in her becoming way too strong with her outplay and kiting potential. There are just more reliable and consistently stronger marksmen people can pick over her as the chance of you screwing up on kalista is way higher than on other late game carries like vayne, luc, or kog.