SOMEWHAT SPOILERS:
I did find the story really interesting, and I have no problems with a story going a complete opposite direction than what most readers want to see. I like stories like that a lot. I don't mind how this story turned out to be -- looking at the narrative isolated from anything else, I enjoyed the experience. However, there's something to be said about fooling your audience. Shock value is a powerful tool and misleading your audience can be super interesting, clever and effective. (Gone Girl is a perfect example of this.)
However, I can't say it really had the same effect here. In a book like that, it made sense and actually added to the narrative...but how does what you did add to the narrative? You misled your audience and mis-marketed your game. Saying "mature" themes doesn't give you a pass to do this, you were purposely vague and misled your audience for the sake of getting people to read and/or be shocked. Your mislead did not add to the narrative, as the shock of what was misled did not add anything to the narrative.
All you did was attract people to this game who may not have been interested in this sort of story and upset them. No one should look into playing a certain theme and getting an experience wildly different they never asked for. "Mature" themes is much too broad and you're very aware of that as the vagueness was intentional. Some people are interested in certain mature themes while not in others, or it can even be triggers for them at worst. (This is something that can be ESPECIALLY harmful to people without proper warnings, this isn't some "triggered snowflake" type thing, seriously guys this sort of stuff can lead to relapsing.) Besides it being tactless, people have busy lives with limited free time and should have the right to have some idea of what they're getting into and spending time on that they will never get back in this short life. If you go to the movies to see "Frozen" with your family, you expect them to actually be playing Frozen, not troll you and suddenly start playing "Final Destination". Would it add shock value? Yes. But not for any of the right reasons and not for a reason related to the story.
You marketed this in a way similar to movies like "Bridge to Terabithia" and "Spring Breakers" marketed their movies. There's a fine continent between misleading your audience through the story and misleading your audience as a misrepresentation ploy. The sudden 180 and shock adds nothing in terms of narrative effect, because the shock plays on the audience on a level past the '4th wall' and not really 'inside' of it. It really gave no effect inside of the story at all.
I think I was only not surprised negatively because I saw the Steam reviews and was spoiled to how it would turn out. Again, I actually really enjoyed the story and don't mind the themes you chose. I even wish the game was longer. (Actually just played a depressing and 'all bad ends' game that totally misled their audience and loved it because they did it through the story.) However, I find the disingenuity very ineffective and not very clever here. It will make people find it hard to trust you in the future and thus want to avoid your art.
I would have no problems with this game's story if it wasn't misleading, because the story really is interesting and almost a non-comedy satire on the whole farming sim genre in general. The novel should definitely be kinetic because the choices are nothing short of worthless save for the very last choice, but that's something that can be overlooked for a good story.