Earlier quoted context omitted.
> What big language features did Rust get in the last few years? const generics, generic associated types
Those are not new features. Those are relaxing limitations on existing features and making things more orthogonal. Rust already has had generics, now you can use them in more places consistently. Similar thing with `impl Trait` in traits.
I know they did ship in multiple stages, and some of those were relaxing limitations (once edge cases were accounted for), but a lot of the work was refactoring large portions of the trait solver and related machinery in order to be able to express completely new concepts (const generics are not just "generics in more places", even though monomorphization may make it seem that way).
The reason why they don't necessarily feel like new features is because they fit neatly into existing features, which is a good thing (we don't need another PHP). But they both took years to implement and were huge pain points for a very long time.