This is great when the stdlib is well-designed and kept current when new standards and so on become available, but often "batteries included" approaches fail to cover all needs adequately, are slow to adopt new standards or introduce poorly designed modules that then cannot be easily changed, and/or fail to keep up-to-date with the evolution of the language.
I think the best approach is to have a stdlib of a size that can be adequately maintained/improved, then bless a number of externally developed libraries (maybe even making them available in some official "community" module or something with weaker stability guarantees than the stdlib).
I find it a bit funny that you specifically say HTTP handling and JSON are the elements required when that's only a small subset of things needed for modern systems. For instance, cryptography is something that's frequently required, and built-in modules for it often suck and are just ignored in favor of external libraries.
EDIT: actually, I think my biggest issue with what you've said is that you're comparing Python, Go, and Rust. These languages all have vastly different design considerations. In a language like Python, you basically want to be able to just bash together some code quickly that can get things working. While I might dislike it, a "batteries included" approach makes sense here. Go is somewhat similar since it's designed to take someone from no knowledge of the language to productive quickly. Including a lot in the stdlib makes sense here since it's easier to find stuff that way. While Rust can be used like Python and Go, that's not really its main purpose. It's really meant as an alternative to C++ and the various niches C/C++ have dominated for years. In a language like that, where performance is often key, I'd rather have a higher quality external library than just something shoved into the stdlib.