heh, the belters would probably not agree with how spacious outer space is compared to living on earth(if they could that is). They keep poundering how fortunate earthers are with all that air and open space and sky. They live very crammed, never sees anything outside their shoebox. Belters rarely left their own rock in their life. I like the traveling scenes/when they are on ships, youre right that you dont get the feeling like I got in example firefly, but it´s mainly because this reality is much more gloomy and just dark/cold whilst firefly travels to differenet oxygen-capable planets and shoot revolvers on the ground like cowboys.
Your comparison with GoT isn´t fair imo. Distances between things is bigger in outer space yes, but every set, every scene is much much much smaller in The Expanse because, yeah, building big **** is costly(for the persons in the world its set in, not set-cost itself)
and obv the budget is prolly in the region of 100x