From what I understand, the coding is such a nightmare that adding or deleting any of it is very difficult. Therefore, Inno has decided to just let it sit and say she's stressed while milking subs for every last dollar.
Sarkath can give you a more in depth explanation about how FUBAR the code is.
There's no point trying to save this code. We should just form a volunteer community project like "Girl Life" or the forbidden mod of 'Free Cities'.
This gives Inno far too much credit honestly. Adding / deleting story is still pretty simple, it's true that meaningfully expanding the simulation is hard, but there's also some easy workarounds there (like just reducing the amount of npcs spawned/simulated) that can buy them tons of time.
They are simply a procastrinator who keeps setting deadlines, then going 'Ah! I still have a few days, it's only a few hours of work, it's fine' and then they're an hour from the deadline and goes '...I can't make it, oh no, well, it's okay, I miss them all the time, they won't be mad if its a few days late...' and a few days becomes longer and...
The more we accept the more normal it becomes for them to keep extending. Truthfully while they're responsible - their loyal fans are partially at fault. Had they made a bigger deal of missing them, they wouldn't have began drifting their standards near this much.
I kind of wish someone made a service like Spotify or Setapp where creators get paid for 'plays' by premium members opposed to getting a flat fee every month regardless of how much they worked. That way their income would be directly tied to content releases drawing people to play again...
Either way, anyone thinking an engine change or the likes will fix this is borderline delusional. Only a change internally to Inno can fix this.
