It’s a transpiler, in the same way that Babel compiles es6 to es5, the CoffeeScript compiler compiles another version of javascript with very different syntax rules and keywords down to es3.
The trade-off is that different camps are starting to speak slightly different languages, they used to be very different but there’s now quite close. It becomes hard to work in teams where people are speaking different languages.
But yes, writing less and / or cleaner code is really the only benefit of these compile to js languages.