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?
It’s not a question of the world being too big or too small, it’s the density of interesting things. A giant world with very little worth doing doesn’t accomplish much, but similarly a small world where you’re absolutely tripping over things that feel like you shouldn’t skip them will also feel claustrophobic.
Additionally, the traversal system can help a LOT here. Even a world that has a lot of wide open dead space can feel good if the process of crossing that space is itself fun. Dune: Awakening comes to mind here, where there are large spans of open desert that you need to cross, but ripping across the dunes on my sandbike was so much fun I didn’t mind the dead ground.
Do you remember LoZ Wind Waker? Maybe it’s the nostalgia goggles, but ripping through the open water just felt good. I don’t even think it was particularly mechanically fun. Maybe it was just the music.