[joshkel]

In addition to the other comments -

TypeScript deliberately takes a "good enough" approach to improving JavaScript, instead of designing an ideal but incompatible approach. For example, its handling of function parameter bivariance (https://www.typescriptlang.org/docs/handbook/type-compatibil...) is unsound but works much better with the existing JavaScript ecosystem. By contrast, a more academic functional programming language would guarantee a sound type system but would be a huge shift from JavaScript.

By analogy, Herb Sutter is arguing that something like the C++ Core Guidelines (https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines), with tooling help in this new Cpp2 syntax, can bring real improvements to safety. Something like Rust's borrow checker would bring much stricter guarantees, backed by academic research and careful design, but would be incompatible and a huge adjustment.