if we look at this like that i must agree with you over Kuroi86
crit multiplies damage instead of countering damage mitigation
main purpose of tanky itemization is reducing the damage taken instead of simply making your hp bar longer
which leads us to a conclusion where crit is actualy more effective vs squishies than tanks (tank has armour so crit without lw wont do that much while squishy guys will cry to the sheer numbers of your ad multiplied by 2.5)
so while it may seem to be equaly effective vs everything the real icing on the cake we dont consider is last whisper ... otherwise tanks shrug an adc like he is a minion
and honestly its easy to see in game
if your sample build is ie+ vamp scept+ crit item+last whisper+finished lifesteal item and ga (ofc boots somewhere)
and you would skip the last whisper over bloodthirster or guardian angel you would totaly lose any impact mid game since enemy frontline gives no damn about your crits as long as you dont gave that blue bow
which leads me to another point which i didnt see before
adc's itemization is so fked up that its impossiible to ballance it as it stands
-they have their almoust exclusive stat allowing them to outdamage anyone else without paying with mana or whatever
-they have one tanks removing item and can follow it up by second tank removing item if it works with the specific champion (im not a fan of botrk on caitlyn)
-they are 100% forced into offensive with maybe 2 defensive options (ga if they delete me fast, banshee if they cc me from a far) which puts their ballance around being able to outrun you while dealing damage or straight out remove you
-and on top of the last point their items scale with themselves meaning that the have barely any diversity (the onlyy diversity is picking a triforce or blue ez), simpl put they lose insane amounts of power if they take items that arent meant for them
those are sewere design problems which kinda kill diversity as much among items as champions (they do the same thing and buy the same items so in s4 it was easy to conclude that lucian does everything better which resulted in nerf storm to oblivion, and many adc's shared his fate before)