I can break one container without breaking all of them? I can run them in isolated container networks and even isolated cgroups if I want to. Docker hides a lot of the core reasons tools like jails and chroot and eventually LXC were created but containers absolutely can do the things you are using vms for if you are willing to learn how they work
I was replying specifically in the context of the original question. Unraid already has their services tooling built out over containers so this person already is probably using containerized versions of the arr services. It would be overkill to go build vms for these services specifically for what you said. They don’t need to be windows or osx, they don’t need hardware passthrough, they don’t need a full kernel.
That aside. You absolutely can run containers as a full isolated kernel and directly map hardware to them. CGroups absolutely allows for those use cases. You may not be using docker anymore but docker is more of a crutch for beginners who probably dont need those things.
One example of this in the real world are COS and Bottlerocket which are literally distributions of Linux where even core is components are individually running under different containers via cgroups. COS runs on every GKE cluster in the world and bottlerocket on most EKS clusters.