Luck in old FF titles usually related to drop rates, or Critical hit chance. You can view that by looking at the wiki page on the FF Wiki.

Thats taken care of in XI by DEX, or AGI(For ranged), and Treasure Hunter as a trait. So if you'd like to think because they had luck in past FF games it must be a hidden stat in XI, then I rebut that they are not hidden, and in fact not LUC at all, but DEX, AGI, and Treasure Hunter.

So its not that they decided to leave it out, they added what you would consider a "Luck" stat through DEX/agi(crit rate), and Treasure hunter (Drop rates). But neither are a real "luck" cause as SE plainly stated, theres no way to program luck, since as a computer game, its done entirely through math, and even things that appear random, have a pattern.

So it falls to again, no, there is no luck in XI, at least not in the sense that its a hidden stat. Theres as much luck in XI as there is luck in hitting 21 in blackjack. Random chance.