There's this concept in game design called game flow, which in simple terms is essentially what happens when a game is both engaging and challenging at just the right amounts to the point where you get immersed in the experience. You can't have good flow without both some challenge and reward.

That's why games that are too simple and/or easy are boring. I feel like that's a very fine line you have to walk if you want to make a "cozy" game. How relaxing is relaxing enough without being boring? You need a minimum of challenge and stakes, because that's makes good games good.