True, container security is something of an issue to deal with, but again, it depends on just what you’re doing and you need to do something of a risk-benefit analysis. I know of a fair number of computer security experts who use Docker for certain applications, and knowing security is literally their job.
It all goes back to using the right tool for the right job. I’ll admit that it’s certainly possible, if not likely, people are using containers when proper VMs are more appropriate due to all the hype around them. However, that doesn’t mean that containers aren’t a useful tool to have in your metaphorical tool belt for scenarios where they are actually useful. That’s also in addition to the useful skills acquired for other purposes if you take the time to learn how they work under the covers.
I really need to look up some of Bryan Cantril’s talks. I know of the stuff he’s done since then, but I really haven’t seen him or his talks since we were in college together (he was a couple of years ahead of me).