well ez is one of the few champions that can 1v5 and ..... you need to carry hard if you want to win solo q matches tbh... Some people are just stupid. Sivir has a really short range, and puts her in danger when she does damage. Ezreal isn't put in danger when dealing damage, therefore he is better in solo queue.

With Ezreal, i can build glass cannon, and just kill everyone...

With sivir, to do damage, i must be in range- therefore putting myself in danger. Doing that, I would need to rely on my tanks and teammates. Relying on noobs in Solo q= fail if you wanna win.