Taleofsonata,
The purpose of an ADC in the current meta is to be able to scale to a more than dangerous level in the late game. One of their primary tools are critical strikes. Crits allow an ADC to make favorable trades against other ADCS (or assassins if they are lucky). The drawback to this is that Crit items offer zero defensive value in terms of stats; so even though the full-crit Vayne can potentially 2-shot your bot lane Tristana, it's a different story if a Garen charges up to her with his Q and Ult up.
If you are tired of seeing full-crit ADCs on the other side, I would suggest foregoing your normal build in favor of heavy armor items (Thornmail for bruisers, tanks and jungle, or damage reduction ADC items like Phantom Dancer and Death's Dance.) If that doesn't work, hope that you have a jungle mumu or rammus. ;)
IMO, League isn't just about building the recommended items (which are usually full-crit for ADCS). It's about building to facilitate your team or counter your enemy. I went full tank Master Yi against a full-crit Yasuo once. He had an early lead, but after Thornmail and Randuins, he couldn't touch me.
Build to counter!!!