That pessimistic view is not shared by everyone who is working on namespaces, cgroups, etc so I think that’s a pretty unproductive comment in this context.
It reminds me of early days in hypervisors when someone would get an exploit to break out of the isolation and someone would dismiss it because “virtual machines aren’t real isolation anyway”.
Look, I get it and I frankly agree with you in the current state of the world, but this is the time to shut up and get out of the way of people trying to make forward progress. Breakouts of containers are a big deal for people pushing the boundary there.