[tobico]

"Fly is a build system for Node based in ES6 generators and promises that aims to be simple and elegant to write and extend"

If an objective is for it to be simple to write and extend, why use two shiny new features that most programmers will be unfamiliar or inexperienced with?

[sanderjd]

The theory is that those shiny new features are simple to write and extend, regardless of most programmers' familiarity or experience with them. I don't necessarily agree with that theory in this case, but familiarity is too often conflated with simplicity, when in reality there is a more nuanced interaction between the two.