"you can't be scared of something you don't really know what it is."
Holy shit this guy is retarded.
Well, he corrects himself in the next sentence.
He meant it in the way that you can't be scared, when you don't even know you're supposed to be scared.
Amnesia's first half of the game was entirely atmosphere. What MADE the first half so scary was the fact you didn't know what was out there, just that you were being followed by a shadow. The notes Daniel leaves behind is what acts as that motivator. He's constantly talking about this "Shadow" that's chasing you.
But while I do agree with most of the points brought up in here, you also need to keep in mind that the game was just a little project someone made over a weekend in Unity. It's not actually supposed to be some sort of major horror game. It just got really overhyped by youtubers like pewdiepie and shit.
Don't blame the game, blame the retards who overhyped it and went "OMG ITS THE SCARIEST THING I EVER PLAYED".