I don't disagree with the premise of your post, which is that time spent on X takes away from time spent on security. I'll just say that I have not had the experience, as a professional rust engineer for a few years now, that Rust slows me down at all compared to GC'd languages. Not even a little.
In fact, I regret not choosing Rust for more of our product, because the productivity benefits are massive. Our rust code is radically more stable, better instrumented, better tested, easier to work with, etc.