Every game I have abandoned had the same fatal feature: a second screen. Once you have a second screen you have a third, and a save system, and a settings menu, and suddenly you are eighteen months in.
The next one fits on one screen. It has no menus. It has no save slots. It is one idea, expressed as tightly as I can manage.
I will probably break this rule eventually. But it is a good rule for now and it is helping me finish things.