But you are also speaking as someone who already knows Rust. If we take a step back and imagine someone who knows neither, what's easier to learn, a high level language or a low level one? (I don't think pointing out that Rust has high level aspects alters the relative situation)

Take two programs with historical success in building this kind of plugin system: Emacs and Browser. The number of non-programmers who can write elisp (or javascript) but won't dare to touch C/C++ code in the core layer probably outweighs the opposite by a huge factor.