I'm Not your... puppy?

How is this game difficult? All you do is press a couple of buttons for x amount of hours to level up. This game requires no skill at all... and btw, it's REALLY easy to "have a life" and still play the game: It's called time management.

This game is not difficult in the sense of requiring high intelligence, or in the sense of requiring exceptional hand-eye coordination. But one thing it does require plenty of: patience.
The ability to keep pressing those few buttons for hours and days and weeks on end, is one not many people have.
Those who lack the patience, but still want to play the game, look for "cheats". Same as with any other game, no matter what sort of skill it requires - people who lack the skill but still want to play, or at least "win", the game, look for ways to circumvent the difficulty.