This is what witcher 3 did best imo.

It's open world, and it feels large... But it's not actually that large when you think about it.

And the side areas are so rich and dense that you can do quests from a random hub, some that chain on for quite a while... And then realise this whole time that you haven't actually done any of the main story.

I was excited to learn more about certain monsters in the bestiary, what oils and elements they were weak to etc.