It's been a few years since I used Flutter, but doesn't it still require you to use the related language Dart? I liked the idea of it, and I thought the tight integration between Flutter and Dart allowed them to do some cool things. But I wasn't a huge fan of the language itself. And I think it's a lot to ask prospective extension-writers to learn a new language.
Rust actually has a library with very good flutter integration, it does require using dart for the actual flutter part though, but it works well together.
