For any systems language, interop with C is the litmus test.
With that in mind, this new language should not require 15,000 lines of standard library. A type-safe wrapper for libc should be enough...
The standard C library is not great. There's a lot of dangerous cruft in there (gets), as well as cruft with various gotchas (sscanf; see the recent hoopla about it being linear in the length of the string even if you just want to read a fixed-length prefix). It absolutely makes sense to design new, safe, consistent libraries along with a new language.
THAT SAID, I shudder at the idea of people writing yet another library for "Hashing • encryption • key derivation • TLS • etc".