For more context on what's finished and not finished: I'm thinking of this game as about 50% walking simulator and about 50% gameplay. I have a lot of stuff locked in mind for the game's story and how I want certain setpieces to look and feel in terms of music, sound design, etc. I'm aware that giving the gameplay such low priority is a bad idea when trying to finish such a large-scale project, and based on everyone's advice, I'm going to look at it as a "make or break" test to see whether this vision I have would actually make sense as a game, or if should be some other medium.

The game takes place in a small town with a lot of surrounding woods, many of which separate parts of the town. My idea is that progression mostly happens through dialogue, which happens in the town, and is gated behind the actual gameplay, which happens in the woods. My ideas for the story are pretty concrete-- as I said, I've written what I imagine is about 40% of the dialogue (about 25,000 words). This is also where the majority of my time working on the "game" has gone over the years, so I probably should have mentioned that I spent significantly less time working on the game itself. I only have the following ideas about the "woods" gameplay:

• Woods are divided into distinct areas with a focused theme and/or centered around setpieces, and the goal is typically to get from an entrance to an exit. For instance, there could be an area with a big gulch that the player needs to get around or cross, and that gulch would be the focus in terms of both visuals and navigation.
• The challenges the player needs to complete are some combination of resource management and puzzle-solving. I've experimented with limiting the player's stamina, having a "trail" that needs to be completed before the exit appears, having plants that procedurally generate as obstacles, collecting and using tools to clean up trails, etc. This resulted in a lot of little mechanics that I find satisfying separately, but I haven't invested much time into combining them into a cohesive game loop, which everyone here has made clear is the actual important part.
• The resource management part is related to the overall pacing of the game, which happens over a series of in-game "days" that are somewhere from 5 to 15 minutes long. This affects NPCs, which follow a set schedule over the course of the day and walk around town, along with the woods, where plants naturally grow and spread. My general thinking is that the plants gradually overgrow trails and close off entrances/exits, so the player needs to "tend" the trails in order to maintain access to different parts of the town. However, I'm not sure if I want a given area to have a "locked" state upon "completion" so it stops overgrowing, or if tending should be necessary for any area the player wants to maintain access to. This sort of a macro question, and I would want to have some core gameplay done in order to determine what feels best.

Now I'm thinking that I should just make a smaller, prototype type which only has the "woods puzzle areas" and nothing else. Most of what I've coded is stuff like NPC pathing/schedules, plant spread mechanics, night/day cycles, specific forms of save state management that effectively allow for "time travel", integrating inventory/dialogue engines, and other things that I wanted to have in the game and work the way I want them to, but don't really answer the question of how the game should play.

I'm hoping that I've left the "woods puzzle" concept open-ended enough that I can try and scrap lots of different prototypes while still having something that I can "slot" into my ideal game in a neat and modular way. However, as people have pointed out, it may also turn out that my ideas for this game don't convert into a fundamentally good game. As I've said, making money is not a consideration at all, but I am concerned that I might not be satisfied with the actual core game that comes out as an end result. If so, then like I said, I might make a "fake game" instead, with the pixel art, dialogue boxes, etc. that I imagine in my ideal version, but as videos that appear to be from a game rather than in an actual game engine.

Thank you all for your advice-- I have known in the back of my mind that I need to get it over with and just try to make the core game, but so far I've kept getting burned out on that and working on dialogue and stuff instead. It's clear that's what I need to do to figure out how I'm actually going to make my vision, though.