I do think SE was attempting to do something new with FFXIII but ultimately ran low on time and money. You can see this in the way things like conversations are handled. Simply stopping near someone will trigger a random spoken line equivalent to a text box in other RPGs. I think a place like Nautilus exhibits signs of what they could have achieved with more towns in the game. I would have liked to see moments like that more often. Palumpolum could have been excellent for this, for instance. You don't need to have shops everyone or side quests, but give the player a visually dense environment to explore leisurely before jumping back into combat zones.
That said, I could see the way XIII ended up bothering people more or less depending on play style. For me, I don't spend all that much time per day playing a game like this. When I play in the evening I might get 2-3 hours in and then call it a night. I'm enjoying experiencing the game in these chunks. If I sat down and tried to play for a significantly longer period of time, however, I suppose the pacing would be much more frustrating.
I must admit, however, that the world feels more immersive to me than something like Vesperia despite the lack of towns. You are limited in where you can go, but the areas you visit still manage to feel quite large and making your way to each new area takes enough time that it actually feels as if you have traversed something. In a lot of RPGs, large areas and towns are represented with small models that give the impressive of something much smaller than it supposedly is. When you visit Palumpolum, for instance, you don't actually see that much of the city, but the way it is visually designed makes it at least FEEL as if you are running around a portion of a much larger world. Seeing EVERYTHING doesn't always make things feel properly vast. Anyone else feel this way?