Depends what games have available to you/price range. I would agree with the Diablo 3 mentions. Also Destiny 2 isn't really hardcore if you're just running the campaign with friends, plus its free ninety nine.
BioWare games have been trash this gen but I liked the co-op in both Dragon Age: Inquisition and the horde mode multiplayer in Andromeda. In that same vein I loved the Ghost of Tsushima multiplayer. All 3 start out pretty easy and slowly up the difficulty as you gain better equipment and level up.
If they liked The Forest, Don't Starve Together is on PS4 too.
For turbo casual, Fall Guys.