It depends on the kind of game you’re making.

If it’s a really logic-intensive game like Factorio (C++), or RollerCoaster Tycoon (Assembly), then I don’t think you can get away with something like Unity.

For simpler things that have a lot of content, I don’t think you can get away with Rust, until its ecosystem grows to match the usual game engines of today.

I mean, you could write your logic engine in Rust (as a library), and do all the rest in a more ergonomic language, with a GC.

Yeah, I think that would be ideal if possible, although often that requires most of the state to be in Rust, and exposing proper bindings to every bit of that state is quite an undertaking.