Why do people say Kalista is weak right now?

I actually just don't know if there are any specific reasons, but, I've been playing Kalista for a week now and she really just doesn't seem that weak... I usually build rageblade first, some lethality/lifesteal afterwards and I play directly around Kalista E Rend, you can outsmite any jungler on baron/dragon and it makes for a damn execution once stacked so many spears (which rageblade makes this a lot faster)