Also a ton of important software was written as a giant mess of spaghetti code, or with horrible security vulnerabilities.
I've never been tested on my ability to not write spaghetti code or write security vulnerabilities in my 15 years doing many many interviews.
Unless you're suggesting that knowing the performance of a loop helps with that?
What I'm suggesting is that "Important software has been written by people who couldn't/didn't do X" is not a very strong indication that X is not a valuable quality that employers should want in their engineers.