You should try writing code, and not relying on libraries for everything, it may change how you look at programming and actually ground your opinions in reality. I'm staring at company's vendor/ folder. It has ~15 libraries, all but one of which operate on trusted input (game assets).
> fundamental benefits of a package manager.
I literally told you why they don't matter if you write code in a sane way.
> doing C-style bindings is actually quite common
I know bindings for Rust libraries exist. Read the literal words you quoted. "Rust libraries are very rarely used outside of Rust". Got some counterexamples?