> This places a huge burden on us to be experts with how typescript works.
Yes, exactly. That's how it is supposed to be. You need to have expertise in the programming language to be able to effectively develop libraries other developers will use.
The author also mentions:
> In effect, we are shifting complexity from end-developers to library developers.
This is not a valid complaint. This is obvious and self-evident; and also true for any lib developer in any language - you can't avoid it. Libraries exist to abstract away complex logic so those devs consuming the library don't have to worry about writing their own implementation - an app can delegate functionality to a library and this has the benefit of reducing the app's maintenance burden and speed up dev time by re-using another developer's work. And for lib devs, this inevitably requires they spend effort to make their library easier to use.