I'm going to have to disagree with that statement. Containers (as implemented by Docker/containerD/CRI-O) do add security controls. Specifically, separate namespaces, restrictions on capabilities, seccomp filters and apparmor profiles.

If you can easily break out of any containerized enviornment, I'd suggest you could register for bug bounty programmes and make quite a lot of money also you can get a reward from Jessie Frazelle by escaping from https://contained.af/

Obviously containers have a larger attack surface than say a VM hypervisor, but security is not an absolute and both containers and VMs have suffered from breakout issues in the past. No security measure in isolation provides perfect protection.