How come knowing how to redirect stdin is un-Unixy?

Pipes are a good tool, and so are many others. Having a good command of other basic mechanisms of the shell is going to hugely pay off, try to have a brief shot if you want [0].

[0] https://www.gnu.org/software/bash/manual/html_node/Redirecti...

No. Useless Use of Cat is sufficiently unidiomatic that there is an award for it:

http://porkmail.org/era/unix/award.html

No. Being smug doesn't make someone right. Especially when the smug person is advocating a special case. Special cases are inherently wrong, even when they "save" a process.

If the most logical syntax is

  grep needle haystack

Surely

  grep needle < haystack

is much closer to that form than

  cat haystack | grep needle

Mm, input redirection with the shell is the very epitomy of basic Unix functionality.

< haystack ag Needle

Will work too, and now it's in the logical order.