Comment by aleph_minus_one

> The real meat & potatoes is all the tooling and content and asset pipelines around the engine

This depends a lot on the type of game that you create. For example, if a lot of content is procedurally generated, for example the map editor can be simpler, and you need less kinds of data formats to import. Also, some genres require a lot more "external content" than other genres. Even if you keep the genre constant, you will find games where the "value proposition" lies more in the game engine vs those where the "value proposition" lies in the assets.

In particular for indie games, you can be much more flexible on how you structure your game compared to AAA titles.