A previous dev has suggested that the GTA 6 map really should be smaller and much more densely packed. Even so, as leaks have ongoing to trickle outside of Rockstar, modders have recreated the GTA 6 map in GTA 5's engine which offers a sense of its enormous scale. https://fatallisto.com/story9872225/not-known-factual-statements-about-grand-theft-auto-6-pc