I'd also recommend getting used to serialisation/deserialisation. Serde for Rust makes this remarkably easy. Writing every setting to a file is simple if the compiler can do it for you, rather than you walking the long way around.
Also there are also a shit-ton of minor logic-changing modifications when you're writing prototype gamedev code, (for example, moving an if statement here or there to tweak the physics of your platforming). These cannot be easily represented in config files, and this is why people attach lightweight scripting languages like Lua to their game engines (so that you don't have to wait for those atrocious C++ compile times when tweaking your gameplay code).
(Ironically, serde is known for its atrocious compile times, which really makes the situation even worse. Because of this some frustrated Rust gamedevs wrote their own serialization libraries such as nanoserde (https://github.com/not-fl3/nanoserde)... but you get the point.)