There are reasons to lock flight, though, unless one can do with flight everything that can be done without it. That includes things like set pieces (imagine some of the killer views moving between plates your first time on the moon in Endwalker); enjoyable auxiliary movement systems like grappling hooks and gliders or, hell, catching a ride on giant flying monster; the dangers that world presents (absent in XIV, so I realize we have no such examples here) and diversity of those dangers' forms; etc. Immediately flight greatly reduces the depth available to zone design unless many careful considerations are taken into account.
Again, for my part, I hate the idea of unlearning flight. My absolute preference has always been the likes of GW2, with distinct mounts, but also to have them persist as combat companions. In such a design, one can curtail the negative effects on zone depth of the unlimited and basically physics-less flight we see in XIV and WoW -- since those mounts do not have unlimited or basically physics-less movement. If your companion-mount consumes considerably more stamina when it has to get you up somewhere, too, then fun little auxiliary movement systems don't lose relevance, even if you may replace, say, gliders with just... your ever-available mount. It'd also adds a further risk element to combat, a potential emotional fixture, etc., etc. The only downside is that it constrains available mounts, since they ought to be unique to each other and must have their commensurate costs for power. Which is why you'd never see it in a game like XIV, where we have flying behemoths who move identically to chocobos.