> One could say the same of installing packages in most modern programming languages instead of writing the code from first principles.

I disagree, because libraries define an interface with (ideally) precise, reproducible semantics, that you make use of. They provide exactly what the grandparent is saying, namely a formal abstraction. When you have the choice between a library and an LLM, requiring equal effort, the library is clearly preferable.

When an LLM is more time-efficient at a given coding task, it can be taken as an indication of a lack of a suitable library, tooling, or other abstraction for the use case.