If you wanted to be generous and take him at his word (which I think is fair), then he basically just never really thought about it during the last 3 years. The artist did the art, the coder did the code, everything chugged along fine. Now that they hit the first major hurdle, he DID think about finishing it up himself, but decided to be overly cautious and leave everything to the coder in order to not mess up his workflow or something. It makes sense as a decision from their perspective (i.e., it's not an outright scam) even though it's one I disagree with.
The guy's vision is basically "I'd rather delay the game for 4 months and stick to the original plan". Hence why he hasn't hired more people, or finished the update himself, or paused the Patreon, or changed anything. As for the code, people criticize FET's because it has the hallmarks of being amateurish, as if written by some random guy who just started coding (gee I wonder why). It's an issue if you're working on a project with other people (who also have to understand your code), or one that requires maintainability (if you need to change something, it's better to change one line than having to change 17 separate ones in files named "asfasfgsafas.py"), but strangely enough neither of those are actually relevant to FET, for reasons described a couple pages back.
In this case specifically, it IS somewhat warranted that the artist shouldn't be trying to implement the entire update himself, because it could lead to wasted time. The more complex parts of the game (minigames, map systems, etc) do actually take some effort beyond "if x == true then y else z" style VN code, and if he went ahead and duct taped something like that together for the next update, it would have to be either thrown out (zero time saved) or reworked (potentially MORE time being wasted rather than saved). Hence my suggestion of "just make the scenes", which you could then tie into the existing game with a single menu that appears at the end of the current content ("sorry guys but the coder is away this month, click here to view scene 1, click here to view scene 13") or release as its own thing like the halloween update. Which he seemingly doesn't want to do either, because it wouldn't be up to par with the "experience" people are used to (so making them wait 4 months is seen as a preferable alternative).
And once again, you can CRITICIZE something constructively, raise valid points or offer suggestions in good faith without being an entitled, foaming at the mouth armchair game dev who takes porn games seriously and needs shut the fuck up and go outside (because I can already see where this thread is going).