Indeed. Sure, they have these features, but only if used correctly while introducing vast more complexity (especially when being executed in a k8s environment,but also executed in plain docker). But, you know what also has security when used correctly? Plain linux.
What about 90% of all images on docker hub executing their main payload as root? What about many images bundling unnecessary software like an init system? What about the fact that even if you rm something in a dockerfile, it is still present, if you execute the rm in a different RUN command? What about every user in the docker group being implicit root on the host since they simply can mount the host's / inside their container? What about the reusing of layers between images like it is even intended?
Doesnt sound like a security tool, does it? Sure, it feels a bit like one, but it was never intended to be one, but a dependency and environment bundling tool which happens to use certain linux APIs which can be used for security. But it wraps lots of abstraction around it.
If you want to use these features for security, access them manually. But, OP said they are kind of a noob. Telling them to just use containers is dangerous and leads to false assumptions.
Source: i work as a cloud/container/devops/k8s expert for over 5 years.
But it's the stuff which is used in nuclear power plants to store the used rods.