I realize this is all coming long after release and likely few care anymore. But SOMA's upcoming release has gotten me revisiting these games.
I was one of those who actually didn't mind the direction A Machine For Pigs (AMFP) ended up going being different than The Dark Descent (TDD) and that TheChineseRoom (TCR) didn't want to straight up copy that game and instead focused their talents and experience in creating something that they knew they could do well. And I definitely had fun with the game overall and enjoyed the time I put into it.
That said, there are some points I think could have been improved upon or expanded further, which may be contrary to TCR's direction, but nonetheless I feel should be considered in order to have made the game more like a "game" as opposed to an interactive story.
More Interactions - I think this was pretty much the biggest criticism of the game from most people. Compared to TDD, there was almost no interactions in the game with the physical environment. Not to say that TDD's mechanics in this area were perfect, but the lack of being able to touch most of the Level/World contributed to the feeling that it was a "Sterile" environment without much "life" to it. In addition it felt there were far too many "artificial barriers" to exploration, with so many locked doors and such preventing the player from going places, something which wasn't too obvious in TDD (or at least, there was a more plausible reason for why those areas were blocked off)
A better Sense of Progression - Despite being a more "linear" game than TDD (which was linear already), I would argue that with AMFP, you as the player did not get as good of a sense of logical progression through the game compared to TDD. Which is funny because AMFP had "You are Here" maps throughout the Factory (and I did like the Artwork symbolizing each Section), but it didn't feel like there was any logical layout thought out to the Map, and you would be warped from here to there without really feeling like you traveled there. It's funny because TDD had no map or markers, but the layout and progression through and under the Castle felt more "natural" than moving through Mandus' plant.
Revealing their Hand too soon - In Horror, I feel it is more effective when it is nebulous and unseen. TDD did well with this by forcing the player not to look directly at the Monsters and thus keeping their appearance shrouded. AMFP however decided to be up front with them and allow the viewer to see them up close and personal, in which case their effectiveness at being scary was pretty much cut to nil (aside from the "Tesla" you only encounter twice). I understand this was a story decision as TCR likely wanted the player to empathize with the pigmen in their horrid conditions and being what they were, but I feel they revealed them too soon. Though I suppose "soon" is relative given the game is fairly short at 5-6 hours. But I feel the "Nest" scene should have been moved to the end.
Missed Opportunities in Themes - It goes without saying that most of the points noted so far are "missed opportunities", but one area I felt was sadly not explored to its fullest potential was the whole "Butcher/Meat Packing" theme and the brutality and raw/visceral nature of Butchery. Actually I thought overall the gore factor was pretty tame compared to TDD (especially the Torture sections) in spite of the location. The only time you ever see any of this at play was in the Pigline/Tripery level and even then it was not much. It was also particularly teasing having all those locked doors in the penultimate level Orgone Complex leading to different parts of the Butchery process, and I'd have loved to see more. Would have added a bit of length to the short game as well if done correctly.
The "Twist" wasn't handled very effectively - In a story-rich game, the poignant and important moments are supposed to stand out. In this case the betrayal of the Machine and the revelation of the deaths of the Sons. Both are revealed simultaneously, but sadly the cutscene utilized did not deliver the intent well. From the almost laughable line of the Machine stating "MORE PIG! MORE PIG!" to the comical models of the twins ripping out their hearts, it's supposed to be sad, but it came off too goofy to be such. Even odder is the animation of the twins ripping out their hearts is used randomly again later in the game as a level transition, again going back to an earlier point of breaking logical progression through the game.
Showing is better than Telling - It's fair to say that TCR relied upon their storytelling skills and writing to divulge the plot to the player, in the form of Notes/Journal Entries and the Recordings. But I feel they went overboard in the amount of writing the player had to read in order to understand the plot fully. Again, In TDD, while there were similar notes, there were also areas where the player was told the "Story" through music/vfx/dialogue cues (such as the infamous torture rooms, we all know what happened in there from how they were portrayed without needing to read anything). Basically in TDD you could mostly get the overall plot without having to read too much, which was not the case in AMFP. Of course one can go too far in the other direction, as I feel games such as Souls/Bloodborne overdo "show not tell" to the point where the lore becomes almost too Cryptic to follow closely.
Anyway, those are my thoughts. If anyone is still around