Surely a game engine = code that supported writing & publishing a single game. Nothing more than that. If an indie author finishes a game on their own steam,

Surely a game engine = code that supported writing & publishing a single game. Nothing more than that. If an indie author finishes a game on their own steam, without using a popular decades-old engine, I want to hear how they've focused their perspective to make it work. (this is the engine the author made: https://github.com/untoldengine/UntoldEngine https://github.com/untoldengine/UntoldEngine)