CoffeeScript solved a lot of those issues. It provided a shorter syntax to e.g. Checking if variable is null and undefined in one short syntax. It created an easy to understand structure of creating classes and a ton of helper methods. It took inspiration from Ruby language and it worked.
It required a few tools but it wasn’t very hard to integrate into team’s development cycle. In fact some would argue (i did) that it created a value through more structure.
A lot of job posts started to include CoffeeScript which may be perceived as a separate technology by recruiters (granted it does require a bit of learning but not much).
A short lived technology (i personally have developed a few things using it ) will leave some confused .