I've seen this discussion on the boards and wanted to give some thoughts.
I am a Diamond player supp main. I love getting matched against non-meta supports, especially when they surprise me and kick my ass. Yes, even if I feel like a noob. I am a defender of non-meta picks, but Ezreal is a special case. He has a combination of 4 huge problems:
* No CC.
* No utility.
* No damage without items.
* No tanky / can't mitigate damage.
And I will add, his damage is outplayable since it's mostly skillshots -> This can be important too. (A big plus of Malz is that even if the enemy is challenger, your ult won't miss if you're in range).
Other non-meta supports (that still get flamed):
* Annie, even without gold and 0/10, can always be very impactful since her AoE stun component is not gold reliant.
* An Ashe provides much better vision than Ezreal, and on top of that has one of the best initiators in the game and + reliable slow.
* A Shaco still has hard CC's, vision & zoning from boxes, a slow from E, and all while being able to go tanky if he wants.
* A MF has a long range AoE slow, high out of combat mobility, AS for clearing wards & reliable harass through minions.
Nearly almost any champion, as random as you imagine, will happen to have something. Heck, even a 0/10 Yasuo support can land a 4-5 man tornado + ult with no items and give your Orianna an easy Quadra, or can save your team with a Windwall (pls don't though).
Ezreal is a rare, BIG exception that has no CC at all, utility, or damage without items. This means that if you are not ahead in gold, you are most likely bringing very little to the table, making games where you are behind frustrating and much more difficult to turn around.
I love non-meta picks and I think many champions can support effectively, but I can see how they should bring at least something that is not gold reliant: either CC, utility, or damage without items. Most supports bring at least 2 of these if not more. Ezreal is one of the few champions that have 0 and even when ahead it's just a poke that doesn't go through minions, and only after getting 5000k gold you add some minor cc granted you rush Iceborn after getting boots, supp item and tear. Many Ezreal supports rush Manamune, meaning the only minor CC they can offer comes around their 20 min mark in game.
Anyway, have a great weekend = )