This game is fun, whimsical and pleasant. I find this relaxing and quite enjoyable. Most of all, I can play it! This is not the tough game that it is made out to be. As a series of challenges sometimes I succeed and other times I fail; When I fail I just try and try again until I get it right. After 3 hours and one major boss fight I haven't yet hit a wall. It's classic gaming but with modern visuals, audio and controls.
Accept the game on its own terms. I think that it's a proper game that is disarmingly innocent.
And if kids can play a Mario game then Knack should be easy.