The original intention of FFXIV 1.0 was to have very large zones with no loading times. Instead of going through a gate and waiting for an instance to load you would seamlessly walk through. Technically amazing. Very taxing on the server.

https://youtu.be/-5SQdyGAyC8?t=841

has a good example of what it was like. I doubt in the 18 months development time they had they could fix all the problems they had. I am under the assumption this problem is still around just well hidden away by the segmentation they did,. The question is how much they can drag out of the game if they manage to rework the networking backbone. It is indeed a pain to do. But it would in the long term benefit the game a lot.