The sanity meter just added some effects, nothing else. I was always crouching and in the dark and besides having my eyes bothered by the effects it didn't immerse me.
Why?
There was no penalty for letting the insanity meter fill up. Just the clicking noises and the camera effects.
This isn't very important when the big events, the ones that drained it all, were SCRIPTED. So you can still have the same effects without the unnecessary meter. See?
And the inventory system, how it was used anyway, was also immersion breaking. Oh, let me open my inventory and take these jars out that I have been somehow carrying all this time with me without being burdened by them.
Both elements made it feel like it was quite obviously a game.
I wish more games used Alone In The Dark: Inferno's inventory system. You literally could only hold what fit in your coat and when you ''opened the menu'' the character just looked down, without pausing gameplay so you had to be careful, and you then looked at the pockets in the coat.
Image of the inventory system at the spoiler