If you're making a new programming language today, the standard library is a place where you should think very carefully about everything you add. Every programmer learning the language will have to be familiar with the standard library, so keeping it small is good. But too small, and programmers will always have to reach for third-party packages without maintenance or stability guarantees. For example, you don't want to have to choose among 5 different libraries to write and run unit tests; the language should define that and it should meet everyone's needs (or be extensible with a small third-party library).

I think the Rubys and the Perls of the world probably choose too much to add to the standard library, and that's where the comment you're replying to comes from. But, while it's easy to overdo the standard library, it's also bad if you underdo the standard library. Tough and sometimes under-considered aspect of language design.