While containers have some useful properties, it was never intended to be, and never really functioned as a strict security boundary. We've duct-taped around that, and it's reasonably good now, but that only goes so far.

Shrink your attack surface.

Use a completely locked down seccomp. Use nsjail or gVisor for containers. Use microvm or libkrun for full OS.

Lesser attack surface is what matters. Virtualization is only half of the story.