TBH, there are 2 things which GW2 is king, no game has done it better, which are Open world environment + cities.

Open world environment:
If you play GW2 or look videos, you can see the amount of thought that has been put into making the zones. The zones encourage you to explore, its just beautifull.

Cities:
If you go to divinity reach youll find a true city. It is vabriant, you hear NPC gossiping but most importantanly a humongous city with large walls and such. I was flabbergasted when I saw it and Im a FF14 fanboy. So I would really love for Square Enix to make humongous cities like GW2 or bigger plus raise the cap at how many people can get into the same city instance. I think increasing it to 500 should make it vibrant. Furthermore, dont make 2 city hubs every expansion, just make one big one afterall you want people to get a vibrant feeling. Just put the tomes seller and the MB in one city and make the city BIG + put in npc that make the city vibrant like Guild wars 2 but on steroids.

Another idea:
Make the maps BIG aswell. Reason for this is that you can make more imposing structures, caves, canyons, fortresses and islands. I havent seen this at FF14 at all and ive been playing since near the end of ARR. I really am of the opinion that people just need a wauw factor when lvling which I havent really experienced when looking at the zones. Ultima tule came close but was more of "k this looks nice" but thats it. I want to be able to show my friends and say: LOOK HOW AWESOME THE ZONE LOOKS!!!! If you look at the stormblood expansion when we knocked on the ala migo city, we had a stronghold at the entrance of the zone but it REALLY seemed like a small camp! So please bigger is better. Imagine a big ass librynth or caves or canyons. Square Enix has to travel the world a bit.

What youu guys think?