Dockers for Windows and Macs do not even use "cgroups" and "namespaces" because these technologies are not available on these stacks -- it resorts to plain old

Dockers for Windows and Macs do not even use "cgroups" and "namespaces" because these technologies are not available on these stacks -- it resorts to plain old VMs. So in a sense, yes, Docker is not just chroot but on the other hand, it is also not just "cgroups" with "namespaces". It turns out Docker is a reference implementation for the concept of containers. But you can replace it with anything that can process images and a "Dockerfile".