In this case, handling all the edge cases and variants, and testing a codemod, would have taken significantly more of my time, which costs quite a bit more than the LLM.
Obviously, a deterministic tool is preferable in general, but it is not always worth bothering with for a one off task.
I usually make the llms do that part for me. Instead of asking the llm to refactor, ask it to write the codemod script that'll refactor, have it test that script, and even have it run it on its own. It's definitely faster and less error prone that way for me.
In that case, your original description of "basically consisted of applying the same steps and rules n times" was misleading.