Ask HN: If not Apache NiFi, what would you use?

I read with great interest the comments here (https://news.ycombinator.com/item?id=23144450), and there seemed to be many who didn't like it. However, I didn't really see alternatives suggested. So I wondered, suppose you have an integration task to get data flowing from one system to another. Are there open source alternatives you would recommend? Particularly ones that are friendly to dropping to custom code where needed, and are friendly to storage in (say) git?