Coffeescript does have useful features, but problems such as the ones I described made CoffeeScript code inconvenient to maintain in practice.

If we weigh the convenient aspects of CoffeeScript against the inconvenient aspects, in the end, CoffeeScript can be an inconvenient language to use. It was the case at least for me in various projects I had to maintain.

Part of the inconvenience was all the JavaScript tooling you cannot use, and occassionally being forced to read JavaScript code generated by CoffeeScript.

Yup, totally agree. In 2012 when we adopted Coffeescript, it was less cut and dry - all the open source tools we love now - prettier, eslint, etc. - didn't exist. So the tradeoff was less obvious then.

I loved coding CoffeeScript on my own a few years ago. Today the thought of having to review PRs written in CoffeeScript by my junior developers is terrifying.