There is no open world that is too big. They can only be too small.

However, the quality of an open world is not predicated on the size of the open world, but rather what is actually in it.

And this doesn’t mean that open worlds must be drowning in content, as the quality of the content itself also matters, and certain worlds that are large and empty can still be interesting due to its traversal being good, or the sandbox nature of a large empty world.

Some of the worst examples of open worlds are the kind that are just filled with isolated little fetch quests; busywork that’s all marked on the map with no element of organic exploration. Or the kinds of open worlds where nothing actually happens “organically” without the player starting it.

The best kinds of open worlds are the ones that emphasise exploration and/or have background systems governing the world in some way (i.e. factions that interact with each other without the explicit involvement of the player).