FG's appeal ended together with Penumbra?

[Soul Reaver]

However I liked the sanity system in TDD. It forced you to use your lantern and it blurred your screen when you stared at the monster. AMFP has no such thing but on the other hand has no night vision, although nothing happens when you stare at a pigman.

Well, I didn't really think of the "looking at a monster"-effect as the sanity system. You had that in Penumbra as well and I think it's a nice feature that makes evading enemies a bit harder. However, I can't agree that the sanity system, that is you have to stay in the light, is a good feature. It's just annoying and prevents you from hiding in the dark. The funniest thing is that the dropping sanity doesn't really have any consequences. Later in the game I just ignored my sanity and eventually dropped to the floor a few times. Then I just got up and continued. There is no sense in that in my opinion.

As a good friend of mine once said: Re-playability is like the icing on the cake. The icing will make the cake sweeter, but it's pointless if the cake wasn't that great to begin with.

However, you can reverse that phrase.
Amnesia was a great cake for me the first time I played it, yet still I'm here complaining about it because it was lacking the icing and all that's left is the pale taste of an old rotten cake when I tried to eat it again later.

IMO, you can't negotiate about replayability in a single player game.
It's wasted money if you buy a game and play it for about 6 hours and throw it in the waste basket after you have completed it because there is no point in replaying it.