Honestly, we've seen "what"you can do in the game in this trailer.
There looks to be action, adventure and mystery throughout the game from that trailer. The traveling doesn't seem different from MGSV. Remember how empty that game was in the overworld? Lots of moving around either by foot or by horse and vehicle. Outside of outposts and other areas, MGSV could be cut into a trailer or snippet to look like it's largely void without much "action".
Ppl are saying the empty areas will be populated over time by outposts/safe houses/buildings and highways built by you and other players. Kinda like no man's sky and fall out I guess.