Make them more dynamic on top of actually challenging (or more accurately make it so all of them can't be mindlessly solo'd by anyone). In GW2, some of its world quests (which are pretty much just FATE copies) can actually effect the zone, the most notable ones probably being the events in Caledon Forest, where one can prevent you from using Morgan's Spiral, or how enemy camps can occupy certain waypoints therefore preventing you from teleporting there so you have to take it back. It's not an ideal way to handle it, especially when having a waypoint being suddenly unavailable is inconvenient more than anything, but they do make the zones in GW2 feel more dynamic and alive. What if certain shortcuts on a map could be occupied by enemy forces, that could be temporarily cleared by beating its FATE? What if there was a FATE that suddenly made enemy beast tribe areas deadlier, so you had to storm it with a Grand Company to prevent a summoning? Again, they're not perfect suggestions, but I feel like tiny things like these would come a long way in making the areas in the game actually feel lived in.

XIV zones always feel so empty, because they're just set pieces for stories. I feel like the Ruby Sea (as much as I love Stormblood) is one of the more egregious examples of wasted space because it has an entire underwater section full of literally nothing but one minor settlement.