I'll do you a couple better:
- Doom (1993) was developed by a core team of seven guys in 13 months. That included developing an engine from scratch and basically inventing the FPS genre in the process.
- Stardew Valley was developed by one guy in 4 years. That includes all art, music, sound effects, story, and dialogue, not to mention he built the whole thing using the XNA framework rather than an existing engine.
The long development at this point has nothing to do with game complexity and everything to do with the fact that the
dev pipeline is fucked. This is not a game made by a team of dedicated professionals evenly splitting the Patreon proceeds, it's two or three full-timers (DC, the coder, and maybe the head writer) and a pack of part-time posers/QA people in different time zones who work when they can find the time. It's massively inefficient and DC doesn't seem bothered by it, so it's unlikely to get better any time soon.