You are right about them being much more than chroot, the ability to limit device access and set other resource limits has been possible since a long time ago. VNET jails, introduced fairly recently (12.0-RELEASE with GENERIC kernel, 11.0-RELEASE with custom compiled kernel if I'm not mistaken), can have their own TCP stack and firewall.

I am not familiar with Linux containers, but I read that FreeBSD jails are much, much different from them. As for chroot, it still plays crucial role in FreeBSD jail implementation.