It is too big when the density of reasons to go there and explore becomes to little.

Personally, I don’t really care for games that have huge maps just to pass through while traveling around. There needs to be a reason in the story for every place to be there.

Every village, town or city needs to be filled with quests and stories, and the space between them as well to a lesser extend. They serve as immersive distractions. They need to be alive.

The map is too big if it cannot be filled with enough stuff to explore and experience.

TBH, I am not much of a sandbox game player and the JC 2 and 3 maps looked nice, but didn’t really invite me to stay and explore a single area for a while, because it the areas didn’t have much depth. I prefer a much higher density of things to do. Each village should have a couple of hours of content, exploring it and the neighboring area. And larger towns or cities even more.

I want to minimize the ‘just cruising through’ parts of maps.

Cyberpunk as well had too much dead space when it comes to stuff to do in many parts of the city.