[themoonisachees]

I think part of the issue is that unix does some things correctly (everything is a file comes to mind) and that implementing them without implementing the rest of unix just means you've made a unix-like that's not compatible with normal unix, as opposed to making something new and using the good parts of things you encouter.

[pjmlp]

Everything is a file is certainly not correct, given that is one aspect that Plan 9 has fixed from UNIX's design.

[pasc1878]

Why is everything is a file a file correct?

It makes some things easier but it is not the only way - so this does need to be justified.