I've been playing for a couple days now. My early impressions are the game is pretty fun, but very tedious/difficult. The controls don't feel that smooth, the boy is always either doing the "almost falling off" animation or not close enough to an edge to climb down. A lot of things like your spices are found just by randomly searching a piece of ground.
It's a struggle just to keep you and the girl alive. The pace of the game is limited by all the things you have to do to not die. It takes some persistence to fight through the difficulties to get to the deeper, more interesting parts of the island, which are quite a ways away from your cave. The game does have depth, as there are tasks the girl can start doing at home, making baskets, rope, etc, as well as a lot more things the boy can do beyond fishing and hunting. There are animal traps and animals that can be domesticated, as well as items that wash up on the beach to improve your cave-home (a bottle for water, a barrel, etc.