It was just that we weren't using Rundeck very effectively. I set it up so that others could run a few Ansible jobs, and so that a slack bot could fire off one of those jobs. The Slack API changed a few years later and our old bot completely broke and I couldn't get it working again without rewriting. As far as other people running them, nobody else seemed to use it. So when it came time to upgrade the EOL OS that was hosting Rundeck, I just shut it down.
But, now we have some Jenkins jobs that would benefit from being isolated from Ansible runs, so Rundeck might be a good way to run those.