Hey - author here.

I agree that libraries for certain things, like MobX/Redux or Formik, may be overkill.

What's more important, though, is that people choose an appropriate equivalent to these libraries. Replace the library, but not the method of organizing state.

For example, feel free to replace MobX/Redux in my post with your own global state management solution. But I recommend replacing it with a global state management solution, not something else.