I think most people simply don't know it exists but it is used [0] and has high use satisfaction as far as I can see.

[0] https://github.com/search?q=lang%3Acue&type=repositories

Top result: examples repo.

It's unusual to have repository that is close to 100% cuelang, as a config language you'll have very little of it in repository but github doesn't have a good way of finding those.