The problem is the unmaintainable code. The game doesn't take that long because of its scope, it's not exactly Dwarf Fortress.

If I remember correctly the code got leaked at some point and it wasn't a fun time for the developer. It seems to me the dev was a beginner with a popular idea, leading to random people on the internet giving him money to work for a long time on a codebase that was too large for his experience and should have been thrown away and rewritten years ago.