Key point is that vim macros are interactive. You don’t just write a script that runs autonomously, you say “ok, for the next transformation do this macro. Oh wait, except for that, in the next 500 lines do this other thing.” You write the macro, then the next macro, adjust on the fly.
> Our initiative began with a monumental task of converting more than 15,000 Enzyme test cases, which translated to more than 10,000 potential engineering hours
Out of curiosity, can you drop into edit session during the macro? It is some time since I last used vim, so I do not recall, but in emacs you can record a macro along the lines of "do A, do B, drop to edit session letting user do whatever, do C, do D". Is that possible with vim macros?
This Vimcast (http://vimcasts.org/episodes/converting-markdown-to-structur...) recording is an example of a quite complex macro for converting (a specific file's) markdown to HTML. At the beginning of the video you see that they save the macro to the "a" register. You can record macros of similar complexity to each of the other letters of the alphabet, to get some idea of the maximum complexity (though I tend to stick to about 3 or less in a single session).
Key point is that vim macros are interactive. You don’t just write a script that runs autonomously, you say “ok, for the next transformation do this macro. Oh wait, except for that, in the next 500 lines do this other thing.” You write the macro, then the next macro, adjust on the fly.