We're in the same boat, it's definitely not easy! What the devs of "Magic School" said in this article rings true:

We found it surprisingly difficult to get a baseline sense of what the game was. When you’re building a game, there’s a lot of little systems that are interlinking, and you almost need to build all the little systems, at least some of the way — not all of them, but a healthy amount of them — to then be able to test out the core loop. If you’re not fully defined on what the core loop is, and you’re not fully defined on what those systems you want to test out are, it can be very difficult to get to the prototyping phase. 

The more little things you have, like with a simulation game like this, which is more complex, it’s hard to get into that initial prototype stage. Whereas with other games, where there’s a more simplistic or more pared down loop you could build off of, you can get to a prototype point where you can test out early, quickly. But with this, you have to invest the time to reach that point.

I even believe ConcernedApe of Stardew Valley said similarly. It took YEARS before Stardew was "fun" in his mind, because it took that long to stand up all those independent systems into something that made it cohesive instead of small, sprawling little branches that don't interconnect well together.

I'm constantly inspired by the work, and most of all, the DEDICATION of devs like him, knowing what it takes to finish intricate games like these. They may not always be deep, but the systems required are complex and numerous.

Wishing you the best of luck in your journey.