Too Long; Didn't Read
Using default exports hurts your codebase readability and refactorability. The first major problem with default exports is naming. You have to think about name import every time you include a function. It's forcing you to come up with a good name when creating a new function, as it's allowed to export anonymous values. You cannot spot right on what's that function is supposed to do. You can suggest a different name in the code review, but it's adding that complexity which could be easily avoided.