This. So much. One thing that new authors can’t have any concept of is beginning to end. Starting a project is easy. Finishing one is hard. Releasing something requires a lot of (often unexpected) late-game crunch work and if someone has never finished a game, they naturally won’t have any concept of the entire “through line” of release.
That’s why I always encourage people to write several smaller things they have better chance of finishing and release them before they move on to the huge epic game they hope to make, because they will learn so much about their own abilities and have a concept of the end-to-end commitment necessary that will assist them in realistically scoping and planning a larger project.
Scope-creep is the devil! This is why it’s best to plan, outline, prototype your entire project and know every system and element you have to include instead of “this is a great idea! I’ll figure out the end as I go!” I’ve done that so many times and shot myself in the foot because once you start, you fall in to the death-spiral of polishing the beginning without any idea of the end - so you’ve got a beautiful foundation and no material (beyond conceptual) to build the house.
The modular idea is also great. I fell into that with Baker of Shireton because I had unknowable IRL issues that might cut into my production time. If you get the base “MVP” part of the cake made and frosted, then you can worry about decorations and another layer, but you’ve got a deliverable whether that works out or not.