I don't know how much you actually tried coffeescript but I find your opinion strange. Coffee wasn't ever like J or anything crazy terse. Its appeal came not merely from making things shorter (it did that, but not by a crazy margin), but from adding a lot of useful things to the language like ? operator, spread operator, destructuring, classes, ranges, better iteration, etc. Almost every coffeescript feature was ultimately added to Javascript (and with very similar syntax) which made coffee somewhat obsolete. Coffee's lack of brackets and semicolons everywhere and @foo instead of this.foo, as well as usage of other features certainly didn't take away any readability or explicitness, if anything - they made it better; the same way those same features make Javascript better and more readable (and, ekhm. "easier to reason about") as long as you _know_ them.
Coffee added really nice and productive language features to what at the time still was a very primitive and simplistic Javascript. It also offered a different syntax to existing and new features.
The first part was great and deserves credit for pushing the language to evolve. The second part made it a terrible dev experience. My experience was identical to the gp: writing it was fast and intuitive, but reading it was much, much worse. Not just reading other people's code, but even my own: my ability to understand my own code degraded not in weeks or months, but mere days. It was so bad, the overall result was a net negative and I quickly stopped using it. I say this as someone who has enjoyed writing code in over a dozen languages, from assembly all the way to Haskell.
