There's a lot of points behind this complaint, and saying it's exclusively about how "vast" the world is doesn't do it justice. It's a big world, that's for sure, that's not the problem on its own. But it's a big empty world which is devoid of life. The space station is the perfect example of this; it doesn't give you any impression that you're playing in a real world. You do your class training in a cubicle next to every other class. Profession trainers have a countertop and maybe a few doodads. It's not a real place, it's a player convenience.