Maybe you just suck at it 
Anyway the tutorial can be quite confusing at first.
You have to touch and hold the screen to swing, as long as you keep holding, you'll keep swinging.
To jump to another vine, you have to let go, then touch and hold the screen when you are in range of the other vine.
If you touch it too early you fall straight down.
But for the tutorial, since you have to land on a rock, you have to touch and hold at the right timing so you can fall down onto it.
Anyway the tutorial can be quite confusing at first.
You have to touch and hold the screen to swing, as long as you keep holding, you'll keep swinging.
To jump to another vine, you have to let go, then touch and hold the screen when you are in range of the other vine.
If you touch it too early you fall straight down.
But for the tutorial, since you have to land on a rock, you have to touch and hold at the right timing so you can fall down onto it.
