This is just a modern problem in all software development, regardless of language. We are doing more complex things, we have a much bigger library of existing code to draw from and there are many reasons to use it. Ultimately a dependency is untrusted code, and there's a long road to go in hardening entire systems to make running arbitrary dependencies safe (if its even possible).
In the absence of a technical solution, all others basically involve someone else having to audit and constantly maintain all that code and social/legal systems of trust. If it was pulled into Rust stdlib, that team would be stuck handling it, and making changes to any of that code becomes more difficult.