The World: so Big so Beautiful... But yet so empty

[Shurrikhan]

They don't had tunnels, yes. But they had canyons

And this was a bad thing? If so, I find it odd that ARR had higher portions of constrained areas than 1.x ever did, and HW and SB still more than, say, old La Noscea or Thanalan.

While the Emerald Shroud, especially in the stretches around Bentbranch and Camp Tranquil had practically become memes, many forget that the Black Shroud also had vast open wade-able misty rivers and multiple levels of terrain that gave it much more traversable area overall than one would expect from the reports of "tunnel, path, glade; repeat". Outer La Noscea is more constrained by comparison, even if certainly a more unique and generally likeable zone. Thanalan averaged to larger expanses than any of its current sections. La Noscea was more open on average than any zones since. Coerthas was something of a middle-ground; the mountains broke and blended it seemingly realistically into rolling canyon sections, especially in the SW corner around the old Boulder Downs or, separately, in the high paths around Prominence Point. Other areas of Coerthas, however, were split only by the rivers or the central gorge and were otherwise unbroken nearly to max sight distance. They were designed to create different moods through the openness of traverseable space, and did so, even if far from perfectly. This is part of any zone design philosophy, not just 1.x's, and you'll find little in that overall take on zone design that you won't find in any other MMOs or in XIV since, save perhaps for a portrayal of Eorzea as a frontier, instead of an arbitrarily populated space.

I'm not sure why people assume that because these zones were large, they must have been thin or largely unusable (or by extension that there was a some sort of cap to traversable area renderable); WoW was able to seamlessly place entire continents into single zones with PCs about the power of a first-generation Xbox. The area itself is irrelevant.

In going from 1.x to 2.0 they simply swapped the copy paste endlessly looping terrain for loading screens, since people complained about the copy paste terrain.

That would only had been the case if assets were being changed across those hallway areas of 1.x's zones. They weren't. In fact, areas where assets were being swapped out were just as often open areas, such in crossing a wade-able stream than ran along either end of the adjusted areas, meaning that both were still being loaded, rather than one traded for the other beneath the obfuscation of a hallway area. The famous loops of 1.x were less often a limitation of processing power as a limitation in budget.