I actually liked playing this for a bit. I was in the Beta test, and got the game on release (with all it's glitchyness)
I don't play anymore because...
1) Action bars are too limiting - 5 buttons (excluding the Ultimate button) is not enough for a game with the depth of abilities that ESO has - please ADD 2 more ability buttons on each action bar. With the expectation that you can play how you want, the lack of ability buttons doesn't truly allow that and adding 2 to each bar would better implement this idea.
2) Building a pure crafter is almost impossible - I'm an altoholic, and I want my characters to have the best gear I can make. Unfortunately, in order to put points into crafting you have to hunt/quest, therefore you have to put points into fighting abilities to quest and level up just to get points to put in crafting. Not only do restrictions come for the character side, but also the material side. If you want a full crafter you need materials. Unfortunately, your bag and bank space is so limited that you can't possibly hold the materials for a pure crafter. At this point is where I quit playing, in order to hold the materials I needed, I had to make 7 or 8 alts to hold materials, which wasn't that bad until you get to many materials, AND have to start switching between multiple alts to get the right materials. The loading screen time it takes to switch is overwhelming. So, increase the material stack number so they don't take up as much bank space, easy fix. Most MMOs out now have 200 -999 stackable.
3) This one might be harder to implement, but would be awesome. Make a grab mechanic for, at least, PvE combat. Imagine a tank charges and stuns an enemy, grabs and punches, kicks, or throws the enemy and then continues combat actions. Or for Assissin types, pops out of invisibility, grabs an enemy, stabs him a couple of times, then kicks him away to continue combat. Games like Gears of War and Blade and Soul as well as many others have this, and it just gives a Massive kool factor to the combat and in a game like ESO would look and feel amazing.
--- I'm not a game designer, so these are just my humble opinions. But, if these 3-4 things were implemented I'd not only come back to this game, there'd be nothing like it in the gaming world, and I'd probably play for years, way more than Destiny, that hulking pile trash.