Starting with Godot 4.0, they now support GDExtension which allows you to basically write your own game code in C++ (and other languages), then have the engine import your code: https://docs.godotengine.org/en/stable/tutorials/scripting/g.... There is also a set of Rust bindings that utilize GDExtension too: https://github.com/godot-rust/gdext.
They might be worth looking into.