> those small, quick-to-make dynamic codebases ended up becoming unmaintainable monstrosities

In my experience, type checking / type hinting already starts to pay off when more than one person is working on an even small-ish code base. Just because it helps you keep in mind what comes/goes to the other guy's code.

And in my experience "me 3 months later" counts as a whole second developer that needs accommodating. The only time I appreciate not having to think about types is on code that I know I will never, ever come back to—stuff like a one off bash script.

Yep, I've seen type hinting even be helpful without a type checker in python. Just as a way for devs to tell each other what they intend on passing. Even when a small percent of the hints are incorrect, having those hints there can still pay off.