Benjamin Olson
Hero
It is a third dice on an attack only when you have advantage and when you are probably going to hit anyway if you ever get to use it. I am guessing it matters maybe once in every 3 days in a non-Rogue.
I find that my tier 2 Fighter/Barbarian, who makes nearly every attack once he closes to melee with advantage due to reckless attack (if no other source is available) still misses about every 6th shot or so (or would if I didn't have precision attack). Obviously this sort of build doesn't qualify for Elven Accuracy, it's just the character for whom I have the most experience rolling lots of attack rolls with advantage in succession in actual play.
In any case, if we figure normal advantage still missing about a 6th of the time is reasonably average then on pure saving attacks numbers Elven Accuracy requires making more than 18 advantaged, non-strength based attacks a day to outpace Lucky, were one to devote Lucky entirely to saving advantaged attacks (which generally wouldn't particularly make sense for non-Rogues). Some characters consistently do that, most don't. Yes it will also increase your crit-chance, but it just means getting a crit on every 20th advantaged attack that wasn't already a crit, which doesn't make much difference on most builds.
The real value is that it's a half feat with +1 to one of four stats, and thus not really comparable to Lucky. It's not worth taking if it doesn't even out an important stat for you. But if it does, and your a character who makes a reasonably high number of non-strength based attack rolls with advantage, it's pretty solid. It doesn't need to necessarily be optimized for it to be worthwhile. I would probably always take it on an Elf Wizard eventually (provided they could make use of the stat bump) simply because turns when you are stuck just casting firebolt are lame enough, you should at least get to do it with your pet owl giving you superadvantage.