And that'd be fine if everyone were on board with it and that were the general direction of the project, but I don't think that's true.
I've never seen a strict, type-annotated Python project out there in the wild, and I've seen a decent amount of them. A random non-primary-contributor isn't going to have much luck stepping into an established project and getting everyone to go along with adding annotations to the whole thing.
And if I were starting a project from scratch, rather than coercing the language to do something it wasn't really designed for, I'd just use a language that has first-class support for types directly in the compiler, like Java or Go.
I've never seen a strict, type-annotated Python project out there in the wild, and I've seen a decent amount of them. A random non-primary-contributor isn't going to have much luck stepping into an established project and getting everyone to go along with adding annotations to the whole thing.
And if I were starting a project from scratch, rather than coercing the language to do something it wasn't really designed for, I'd just use a language that has first-class support for types directly in the compiler, like Java or Go.