I have recently done an engine rewrite for my sequel game and I very much agree with this. In my postmortem[1], I wrote:
> Most people think of a “game engine” as code that is shipped with the game executable. However, that’s only half of it. The other half, which I’d argue is more significant, is the code that is not shipped with the game - level editors, content pipelines, debugging/profiling tools, development workflows, etc.
Writing tools is arguably more boring and tedious compared to writing an engine, and that's where lots of "making a game with custom engine" type of project grinds to a halt
> Most people think of a “game engine” as code that is shipped with the game executable. However, that’s only half of it. The other half, which I’d argue is more significant, is the code that is not shipped with the game - level editors, content pipelines, debugging/profiling tools, development workflows, etc.
Writing tools is arguably more boring and tedious compared to writing an engine, and that's where lots of "making a game with custom engine" type of project grinds to a halt
[1] https://ruoyusun.com/2025/04/18/game-sequel-lessons.html