There are already some huge maps out there, Just Cause 2 and 3 both have maps at around 1000km2, and those games are beloved by their players. But if the next Cyberpunk game was announced with Night City now being the size of an actual large metropolis, say like New York, would you say that’s too big? What determines what “too big” is?
This is it.
GTA 5 was boring when it came to exploring, much of it was pretty empty unless there was a mission. Elder Scrolls Arena was just random generated repeated stuff - miles of it. Assassin’s Creed Odyssey was a lot of copy and paste.