Repetition:
There wasn't
that much repetition. And why did you even mention water? There was only one instance where being in the water was any kind of threat, and didn't it succeed in turning you off water for the rest of the game?
If you think about it most games are repetitive: the majority of action games consist of you walking into a new area, enemies spawn, and you kill them. The trick is pulling off the rest of the game well enough so people don't notice the repetition so much.
Call of Duty, for example, relies on keeping the player constantly alert to any situation they find themselves in in order to stay alive.
Devil May Cry has a fun combat system that keeps the player occupied with stringing together new combos & raising their style rank.
Amnesia creates a truly tense & immersive atmosphere that keeps the player on edge throughout the entire game - they're too busy worrying about what could be around the next corner to pay attention to level design.
Interactions:
Why can't he lock the door? Because he'll have to unlock it again when he goes to leave, and locks don't stop monsters from breaking in since they usually tear down the entire hinge. Why can't he break a random door? Because Daniel is not a tank; if he was he wouldn't have to be cowering in dark corners. And reading books... really? Do you have any idea how many books there are in the game? Do you really expect the developers to write something different for each and every one? This isn't
The Elder Scrolls, this is a short horror game by an independent developer who don't have the resources to sit around typing literature that would be overlooked by most players (people don't play videogames to read books - there are BOOKS for that).
Why would anyone want to UNDO a puzzle they spend ages trying to solve? Once a machine roars to life most survival horror players would avoid touching it at all costs in case they happen to fuck something up. As for using puzzles for "frequent things"... I thought you wanted to avoid repetition? And which Amnesia player honestly wants to extinguish an environmental light source? In fact I believe it's the times when the lights go out that players get truly tense.
The reason you can't injure or scare monsters away is because the player is supposed to feel weak & vulnerable, you're missing the point entirely. You can in fact throw objects at monsters to stall them a little bit, but how many of us take the time to do that instead of just running away?
There's no point in giving enemies idling animations since the player is supposed to avoid looking at them entirely. There's only one instance in the game that you can actually sneak up on an unaware stationary monster, and even then you can barely glimpse it before you slowly go nuts.
As for friendly NPCs:
1. The player is supposed to feel alone and helpless in Brennenburg.
2. Programming friendly AI is hard.
The inventory:
The inventory does what it's supposed to do, and nothing more. It's simple and effective. The inventory system in TES wasn't that far advanced anyway; the most you could do was drop items on the ground only to be picked up again. And the only reason you'd want to drop something was if it was either useless or weighing you down. Since Amnesia doesn't have an encumbrance meter and EVERYTHING you pick up has a vital use, there's no need for a drop feature. And who really wants to backtrack several levels just to retrieve an item they dropped and didn't realise they'd need later? The developers were careful to design the game in such a way that the player was unable to progress until they had found all the unique items in that particular level, which encouraged thorough exploration.
The Lantern:
Again, the lantern was simple and did what was required, nothing more. Who really wants to rely on a light source you had to pick up and carry around everywhere with the mouse button, having to put it down while you interacted with a door or drawer and hope it didn't glitch into the map geometry?
Game flow:
Most players are glad to finally be out of the previous area, what with the Shadow & creepy monsters & all. With the atmospheric gameplay being primarily exploration-based it's unlikely that players would miss anything of any importance, making backtracking rather pointless. In fact backtracking is something that should be avoided in games as it's a sign of lazy design (see
Devil May Cry 4 level design).
Game "flow" is exactly that - it flows in every direction except backwards.
Game flow 2 and Guns/New Items:
Tinderboxes and oil aren't necessary items for completing the game? Have you completely forgotten about the Sanity mechanic? Without light you'd spend half the time dragging your face along the ground, which you wouldn't find much fun I would wager. As for the "fantastic Night Vision", I think you're confusing this game with FG's previous game
Penumbra, in which you could survive quite happily on night vision alone (which I did on my first playthrough because I was afraid to use any light sources for fear that I might be spotted). The great thing the developers addressed in
Amnesia was the use of light sources; forcing the player to stay in the light and avoid the dark as much as possible, unlike their previous game where (ironically) players could feel safest in the dark.
And I thought everybody was clear on why there are no weapons in the game, especially guns.
Mapping and Scenario:
I'm not quite sure what your main criticism is here, one of the things the level designers got well was that each level had a unique look & layout such that you can easily recall your journey through the castle, or see a few seconds of gameplay footage and immediately know what part of the game it's from. I don't see how exterior mapping would improve the game and it would bee a wasted effort; so much effort for so little gain. The atmosphere is such that people are too focused on what's going on inside to worry about what's outside.
Story telling:
Because this style of storytelling suits the gameplay & atmosphere; you're alone in a mysterious place and have to piece together clues you find in order to find out where you are and what's happening. It just wouldn't flow with the rest of the game if you have some NPC blatantly tell you what's going on. And, as I've mentioned before, programming friendly NPCs is hard and this is by far the most cost effective means of storytelling. This is a small company after all, and they're very resourceful with what they have. Always remember K.I.S.S: Keep It Simple, Stupid!
Plus this style makes a refreshing change from most current games that practically hold you by the hand the whole way through the plot and treat you like a child with ADD.
Horror:
There isn't much to complain about in terms of horror, as I'm sure 102% of the population is aware, but a lot of your criticisms seem to attack the very things that makes
Amnesia scary: mysterious atmosphere, limited resources, reliance on light, keen observation, utter helplessness, etc. This game focuses heavily on establishing an oppressive atmosphere, which it does in ship loads. You only need to focus on enemy variety in games such as
Dead Space or ones that focus heavily on monster encounters, which
Amnesia doesn't. In fact the player isn't even supposed to LOOK at the monsters, further eliminating the need for a variety of character models you aren't supposed to see. Again this adds to the atmosphere of the game; people are generally more afraid of that which they cannot see.