Maybe "not maintained" was a bit harsh. Until end of 2020 ThoughtWorks spent a lot of resources on developing new features. This has stopped now, so I'm a bit concerned that while GoCD seems to be actually maintained (there are some very recent bugfix commits in the repo), general development of new features might be slow/nonexistant in the future.
Here's the official announcement: https://groups.google.com/g/go-cd/c/EXwfvZZeLrM