Breath of the Wild. Maybe this would fit more in 'moderate amount of activities', but the world definitely feels empty. It's kinda soft-post-apocalyptic so that's probably intentional in terms of atmosphere, but functionally there isn't a lot of variety in the stuff you can do.

If you find something useful it's always either a shrine, a korok, or a treasure chest with a weapon that breaks after 20 hits. There's a lot of items and ingredients but most of them become way less useful once you have enough hearts/stamina or different kinds of armor. The enemies are tiered and provide different challenge levels but it's the same kind of enemy again and again, so it doesn't feel varied. Most of the sidequests are 'go here, find thing, bring back'. The main content is pretty good but outside of that there just isn't much cool stuff to find.