Docker is a concept resembling FreeBSD's jails that were introduced in year 2000, having much better isolation, much better security than Docker has had for a long time (perhaps even now jails are still superior to Docker).
Better isolation, better security, but far fewer gists and shared config-files shared ok the Internet for common tasks. Docker comprehensively wkn thr popularity contest, and is often the more convenient solution because of it, in a worse is better way.
People comparing Docker and Jails don't really understand that Docker is 99% about packaging and composing software. From that perspective Jails are nothing like Docker containers. No versioning, no standard, no registry, no compose, no healthchcks, no tree of containers, etc. etc. etc.
If you want to compare Jails to something on Linux then I think LXD is probably much closer to what Jails are.
