Phantom Dancer is the only counter to the ADCs meta atm.
Ironically, it builds out of a recurve bow, the most contested item in the game, making it too difficult to get one, let alone multiple phantom dancer.
What about Thornmail and Glacial Shroud you ask? They are both bad against ADCs. The armor they give is too low given how much damage ADCs deal. Glacial Shroud effect only affects nearby enemies when ADCs won't be in reach. Thornmail effect doesn't scale well and quickly becomes unnoticeable.