Canonical has a tradition of inventing something that’s ahead of its time only to see nobody else is going the same way as they are. Sometimes they realise it was a mistake and follow everyone else.
Juju had a different problem: it was big-bang rewritten in Go and that froze features for too long for them to keep their mindshare. Rewriting was the right decision, as Python had poor concurrency back then, but doing that while freezing features was a mistake.