It reminds me of companies I've worked with before that accidentally had a production site pointed to a dev database. Why the hell is that even physically possible with your network setup?
Anything can reach anything, provided you know the naming schema... and there's no easy way to fix it on anything that is not AWS/Azure/GCP, not without losing all the benefits of a self hosted k8s cluster in the first place.
Openstack at least provides ways to isolate machines, but that's VM-level only and truly an ultimate PITA to set up.
Specifically can you go into more details about what worries you with containers. Is it insecure images with out of date software, or risky applications inside the containers? Something else?