I disagree, as I see it Rust's core-lib should be to interact with abstract features (intrinsics, registers, memory, borrow-checker, etc), and std-lib should be to interact with OS features (net, io, threads). Anything else is what Rust excels at implementing, and putting them into stdlib would restrict the adoption of different implementations.
For example there are currently 3, QUIC (HTTP/3) implementations for rust: Quiche (Cloudflare), Quinn, S2N-QUIC (AWS). They are all spec compliant, but may use different SSL & I/O backends and support different options. 2 of them support C/C++ bindings. 2 are async, 1 is sync.
Having QUIC integrated into the stdlib wouuld means that all these choices would be made beforehand and be stuck in place permanently, and likely no bindings for other languages would be possible.
I think Rust really needs to do more of this. I work with both Go and Rust daily at work, Go has its library game down -- the standard library is fantastic. With Rust it's really painful to find the right library and keep up for a lot of simple things (web, tls, x509, base64 encoding, heck even generating random numbers.)