I'm not sure what you mean, I think we were discussing upstreams (such as Bootstrap or whatever) supporting old browsers?

The old browsers are presumably (according to that page) still getting security updates by Microsoft, so I'm not what you're arguing. (Either way, if the browsers are not getting security updates, that's on Microsoft, not on upstreams.)

Can you explain what you mean?

EDIT: Hopefully to clarify what I'm puzzled about: How is having to use an old Bootstrap a security issue?

If you're thinking ATMs it's not such a problem because they are not connected to the internet and if bad guys get physical access it's pretty much game over regardless of the OS.