Ezreal is mostly just strong against bad players. The good ones know to just stand behind the minions and harass. And that's really a big problem - Ez is a ranged carry that gets outharrassed by every other good ranged carry. If you're building AD, he has nothing that goes over minions except for his autoattack, which doesn't have a very long range. If you're playing AP, you'll have mana problems trying to hit with W (and AP Ez isn't so great anyway).
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Black Turtle did a pretty good job.