Anything written in interpreted languages like Javascript/Typescript.
UI stuff usually has hot reloading where you get "compilation" times measured in milliseconds, and from experience restarting even a complex typescript server is a few seconds max. This applies to mobile apps as well when using React Native.
I don't quite get your point. Your parent was pointing out that there are interesting projects where the "compile" time is milliseconds — at least for the developer perspective. It doesn't really matter that there's a step later in the pipeline at takes longer, so long as it's not in your way. Also, most of that could be cached away anyways.
Those are all earlier in the pipeline, required for the project to run, and gulp doesn't cache (or, didn't back when we used it), which IMO was the main reason webpack beat it so quickly.
