Prey.

They really put the immersive and sim in immersive sim. So much player agency over the world and everything you do in it just makes sense. The computers you use are physically interactable, no UI as dressing. Your menus are just you accessing your handheld smart device (inventory, logs, map).

Every object on the map is persistent. You want to fortify your office to fend off Typhon on your return? Gather the turrets around the map and have them guard the staircase leading to your little paradise. Want to decorate it? Drop items from your inventory and drag them around. Have some trophies of your accomplishments.

I could go on and on about other mechanics like the fantastic gloo gun or how the maps are filled with little secrets/shortcuts, but then I'd be here all day.