I was a big FreeBSD user, using Jails a lot.

Docker is solving the distribution/setup/resource logistics with a good ux. Jails doesn't solve these problems.

Technically Docker is a huuuuge mess.

Linux has lxc, wich is much closer to Jails afaik. You get a VM-like container, owned fs and setup your "os" yourself. This has pretty much bare metal performance.

I love FreeBSD, but I'd also enjoy some modern comforts in declarative deployment.