and there’s a well-defined mission in each zone

It’s been a long time but I remember there being missions with scripted events and objectives and stuff, but then also areas where the main thing to do was simply travel through it to get to other places. My favorite moment from the game was when I worked out that you could skip a portion of the normal progression by getting to a higher level area early to buy more powerful equipment, but actually getting there was a real challenge due to being underleveled and the difficulty of getting past enemies without killing them. I got a group to make the attempt (which took some explaining and persuasion because it wasn’t the normal next thing to do) and we spent hours on it and got to the last leg of the journey, but ultimately had to give up because our death penalties were stacked too high to get through that last bit. I was able to make it on a later attempt with a different group using character loadouts more specialized for the task.

Something I think GW1 did really well was doing various things like this to build up a sense of location and meaningful travel, which does a lot of work to compensate for the gameplay itself happening in isolated instances and making the world of the game feel expansive and epic.