They do not want to make something irreplaceable. Look at Everquest’s Necromancer Epic 2.0, EQ introduced the 1.5/2.0’s a decade ago, yet serious necros still use that item (despite it having no Heroics and literally 8-10% of the stats of current gear) because of the effect. That’s the exact situation that FFXIV Devs want to *avoid*.

They have also touched upon the “illusion of choice” - if you have three roughly equivalent pieces of gear (same primary stat, same physical/magical defense) that contain different secondary stats, there is numerically exactly one optimal choice. Make the three pieces too far apart, and two of them are lesser choices; make them too close together and there’s effectively no difference between them at all. Either way, the choice is moot, and thus illusory : either there is only one real option to take and the others are not worthy of consideration, or the lack of difference makes it irrelevant which is chosen.