They should have taken a leaf out of XI's book. That had a mixture of both open zones and tightly packed zones and also had lots of little interesting nooks and crannies with things tucked away for you to discover while you explored.

They started on the right track in 1.23 with places like 'Shposhae' that were open dungeons that anyone could run into and had things to do inside like NM's, quests and treasure chests, but now 99% of things are instanced which completely takes away from the world size. In fact; if all the instances in ARR were made open world and you had to at least teleport to a camp then run to them, the whole world would feel much more alive and much bigger.