One way to implement Rust-based “plugins” is to turn the whole application/plugins relation on its head: Publish the main application as a crate, which lets the user build their own executable that uses the main application as a library. That way they can customize the app however they like, if the main app just has hooks for it.
It sounds like you have the mindset that you have to learn programming before you start doing it. Which is especially hard today as there’s so much information, so much to learn, so many tutorials to watch. There’s always something to learn. Don’t expect to reach a point when you “know” programming.
Instead try this: Stop practicing and start programming. Start with a project that you want to do, for whatever reason. Some small utility, a really tiny game, a joke program, whatever that gets you to focus on creating something rather than learning something. You will learn the things you have to learn in order to progress on the project. This is completely normal, and a good skill to have, even for professional programmers.