His previous coder tried to remake the game in Game Maker and bailed halfway the conversion. Besides, the coding for this game is incredibly repetitive, boring, prone to fatal errors etc because of how ancient and shitty the engine is.
I am not trying to say you are a lier, but the second part of you argument makes no sense, there is nothing hard about this game code or the story design or how it relates to the engine, even the engine itself it's not the one to blame. It's just a simple, linear, event-based story.
I used to think like you, but playing games like Fear and Hunger and tinkering with RPGM made me think Ranero don't want anybody else working with him for some strange reason, but the coding it's not the problem, maybe Ranero has a real problem getting around issues with the engine, but for most people, not even professional coders,but just amateurs on RPGM forum, making a game like this wouldn't be a problem at all on the programing side of things.