Have you argued yourself to "it's a bad thing that the Go standard library has a cryptography library"?
If Rust included a crypto lib and a vulnerability was discovered, many fixes are backwards incompatible. Rust maintains strict backwards compatibility, which means updating the relevant crypto functions in the std lib would necessitate a major version bump. By keeping crypto outside of std, it allows the community to make backwards incompatible changes at a higher pace.
Python handles backward incompatibility changes via multi-year deprecations. I'm not familiar with Golang but a quick Google search reveals that it deals with this by using feature flags via GODEBUG. Excessive feature flag use is a bad pattern in my experience years ago, but I don't know if that's applicable here.
I prefer the trade-offs of a "choose your own lib" approach, but I understand the advantages and preferences of those who prefer a "batteries included" approach.
Crypto is something any modern language should include in the stdlib, imo.
Certainly, that's a better outcome than just providing bindings to OpenSSL, which is what most other languages do.
Let me be the first to point out that this is not an easy thing to do since it depends heavily on the community/team/maintainer dynamics. Even agreeing on the goal or scope can be really hard. But if the Rust community is as good as people say it is, that should be doable, right?
On the other hand it wouldn't have to be definitive and exhaustive. Just a safe default. Like http muxers in Go: the one that came with the standard library was fine for a lot of uses, but people generally used third party muxers. I certainly did. And then one of the most used third party ones became shaky as it was no longer being maintained (now it is again, I think). Eventually the one in Go was improved to where I'd prefer to use that since it represents a "safe default" (and I am probably not going to need whatever extra features or performance third parties can provide).
Also note that I see myself first and foremost as an _engineer_. I care less about purity in theory than what things mean in practical terms. And in practical terms I appreciate Go for having so much useful stuff in the standard library. Stuff I kind of think we should take for granted in any serious language today.