My personal experience with things like Flow, Typescript, Typed Lua, and other things I've read from other people, leads me to kind of think that the whole "gradual typing" thing is a ton of b.s. snake oil. At least for language ecosystems that were not developed from birth with it in mind, in place.

I mean the idea that you can take some dynamic code and magically turn it into statically typed stuff one little bit at a time seems empirically very unrealistic: it is the old pulling a thread from a sweater thing; the old domino theory thing; the old fool me once thing; the old pull my finger thing; where once you start you cannot stop (if you want the static checker to, you know, accept the code) before putting in all sorts of even more extensive annotations. Or, hacked typecasts to try to prevent the checker from doing the kind of checking it was built to be able to do. Etc.