No. The whole point of Julia is that the standard library is not privileged — user defined types and functions can be just as fast as “built-in” ones.
There are lots of packages implementing high performance functions, often beating compositions of stdlib functions!
The simple fact is that the standard library is finite. There are plenty of useful functions it doesn’t contain. And there are downsides to including something in the standard library as opposed to a package. Not only can package development be more rapid, but packages are more free to explore different APIs than the standard library (which is locked in by backwards compatibility for all 1.x releases).
It’s not clear what the best API for “negative” indexing is so this is a good topic for packages.