In your wallet, a $5 bill is a capability, you can't accidentally give away your car by handing someone $5. It stands alone. There's no way in a computer to just give a program access to ONE file, at run-time.[1]
Because we don't have capabilities, our computers have to blindly trust code, which is why we have virus scanners, which can't actually work in all cases.[2][3]
So, in effect, we can't trust our computers. Which means we effectively must ride the upgrade/security updates treadmill to try to stay ahead. Which forces things like the Python 2/3 breakage into our lives. The amount of badness from the simple inability to do what you could previously do with an IBM PC XT with dual floppy diskettes is maddening to me.
But I keep pushing, and trying to figure out ways to make the case, and help raise awareness. I hope it helps. Otherwise I could be learning about kinematic mounts[4] or something else fun.
[0] https://en.wikipedia.org/wiki/Capability-based_security
[1] I know about app-armor which isn't really a capability based secure system.
[2] https://en.wikipedia.org/wiki/Halting_problem