You need the right kind of challenges to encourage child’s abilities. But not every challenge need to be as hard as the other. You obviously need some difficult ones but the beauty in simpler ones is that they build up kid’s self-confidence. So they will feel that they can solve problems and that’s a valuable lesson going forward in life and studies.
So, you shouldn’t be worried that some task (for example puzzle or maze) is too simple, as long as you keep an eye on the balance! Remember to take into account things they are doing in school: If school is difficult at the moment, maybe something simpler at home for balance and vice versa. That way your kid will build up both self-confidence and new skills.