But I absolutely hate maintaining an old Clojure codebase (unless it's tiny).
The REPL helps a lot with discovering what the proper way is to call any random function you have in your code, but this is still really super annoying. I really hate to get into a dynamic-versus-static-typing debate, but I've long since come to the conclusion that -- all other things being equal (hah!) -- if I have to dig into a large and old project, I'd much rather have types by my side than not. Code will not ever be adequately documented or commented (and even if it _seems_ to be at first glance, you will always have nagging doubts about how up to date that info really is). This is where type definitions help to figure out the shape of the data that any piece of code is working with. People talk about adding spec/schema definitions but that doesn't solve all the problems with not having type definitions unless you add these spec/schema definitions _everywhere_ ... and let's face it, you just aren't going to do that in any Clojure project. So, best case scenario is you still have a large collection of functions in your project that are calling each other, etc that you are left having to deduce yourself what this random map or list actually contains.