Rewriting something like OpenSSL isn't exactly trivial for many of the same reasons rewriting a large, widely used software library (especially one written in C

Rewriting something like OpenSSL isn't exactly trivial for many of the same reasons rewriting a large, widely used software library (especially one written in C) isn't trivial. Except in this case you need cryptography experts that are familiar in Rust (or whatever language) to review the code. As a developer you should use prefer libraries written in safer languages (Rust, Go, etc.). But that's not always possible given business/environment/etc constraints.