There's a limit to how "lean" a safe, low-level language can be. Rust is leaner and simpler than Swift but not by much, and pretty much all of its outward features are "load bearing" to a far greater extent than Swift's.

(People have tried to come up with simpler languages that still preserve safety and low-level power, like Austral - but that simplicity comes at the cost of existing intuition for most devs.)