Itemize against AD casters

Against AD casters (ezreal, riven, irelia) there is no targeted itemization (like adaptive helm for sustained magic dmg). They do not use attack modifiers (ninja tabi, thornmail) and they do not rely on attack speed (frozen heart, randuins, thornmail).

Riven and Irelia are melee so there are ways to deal with them that don't require itemization. However Ezreal is a ranged poke champion with an escape. Which, after you try to kill him, he uses to aggressively chase and kill you because his sustained damage is impossible to deal with.

Unlike burst mages, getting a pick on Ezreal basically requires him to missplay, and there is no such thing as a tank championing themselves and forcing ezreal out of a fight like with other ADC. If they try that they can say goodbye to their health bar and they better hope ezreal missteps while he is cleaning up/peeling the rest of your team.

You can better champion against Vayne the proverbial tank-shredder. Despite all appearances of her kit she can be itemized against, you can have kill threat, and even if you are dying to vayne she is very vulnerable to re-engage because of her range. Ezreal doesn't have that kind of trade-off in his kit, after three items he outscales everything.