I think it's the natural state of affairs for a "folk standard library" to emerge. I don't think pydantic or serde should be part of their standard libraries. But I will use them in most projects. In ten years, the "folk stdlib" will probably be a different set of packages (perhaps a superset, perhaps not). Don't push the river; if it's natural, manage it rather than fighting it.

Trying to anticipate all or even most use cases in the standard library is a fool's errand (unless we're talking about a DSL, of course). There are too many and they are too dynamic to be captured in the necessarily conservative release process of a language implementation. Languages should focus on being powerful and flexible enough to be adapted to a wide variety of use cases, and let the community of package maintainers handle the implementation. Think of this as a special case of the Unix philosophy; languages should do one thing very well, not a million things unevenly.

I bet most people here don't believe a command economy could ever work in a market for goods and services. Why should it work in a marketplace of ideas?