Why do people say Caitlin's midgame is shitty?
I'm not seeing it. With only two items - IE and PD (Shiv if you're one of those penny pinching types) she completely decimates in team fights. Sure, she may not have huge AoE burst like Graves, or long range, spammable poke like Corki, but with only two items her single target DPS from 650 auto attack range is insane. Plus, she has good utility + mobility, waveclear, and poke. Even with just an IE or BF + Pickaxe, her Q and R are very strong poke tools.
, the only thing that makes her remotely an ADC is her AA range and her naturally high AS.