It depends on the player. Ezreal is one of those odd carries where he can do a ton of damage, but I feel like most people don't know how to do it (I know I don't).
I had a game as support where my ADC picked Ez and I picked Nami cause we needed some peel from Rengar. He told me to take E first and max it. I was kinda skeptical but figured I'd try it and if it doesn't work out I'll just go back to maxing heal. He actually single handedly won bot lane, a feat I haven't seen before with an ADC. Normally the support is the reason that bot wins or why your carry is doing good, but all I had to do was put E on him and he would dodge Blitz hooks and stuff and put both enemy laners down to 200 health from full if not fully kill one of them.
Strangest game of my life but he certainly knew what he was doing even if he did over extend a few times and die. If I get an Ez like that, I don't mind cause he knows how the play the champ. If I get an Ez that spends all his mana on Qs, misses everything, and then blames me when the enemy engages and he doesn't have mana to E away, then yeah, it's frustrating.