A former dev has advised that the GTA 6 map really should be lesser and even more densely packed. Even so, as leaks have ongoing to trickle outside of Rockstar, modders have recreated the GTA six map in GTA five's engine which gives a sense of its large scale. https://gta-six-logo31963.creacionblog.com/35188576/considerations-to-know-about-grand-theft-auto-6-map