Ivalice isn't even a proper setting, or rather it's several extremely different settings with inconsistent lore. Really it's just a brand for Matsuno games. Plus we've had more Ivalice games than every other FF world except VII. So yeah I'm good giving it a rest.
I'd argue that it's because of that incomplete perspective and vast unknowns that Ivalice would make a prime target for revisiting, even more so because it has two totally distinct settings in-universe separated by millennia. (Tactics' more grounded medieval setting, and XII's diverse and advanced golden age.)
Vana'diel is similar in that respect, with multiple unexplored continents with tantalizing lore. Obviously that would be more ideally suited to further expansions... but SE seems reluctant to invest that much despite XI's continued life and popularity.
Most other FF settings on the OP's poll, we've explored the entire world. That was an advantage of scope that older entries had, but it also stymied the need or desire for sequels to their settings (by design, considering FF purposefully never did direct sequels prior to X-2). That's not to say that there
couldn't be cool new stories set in the World of Balance, Gaia, Spira, etc., but frankly they don't have the more extensive existing lore and unexplored areas of Ivalice or Vana'diel, so why not just go to a new setting, since we've seen everything (at least as it was)?