When an interview process produces the output 'doesn't know how to do basic things' on a "vast majority" of experienced people who've been doing said things daily for years, the most obvious conclusion is that the interview process is flawed.
I think it's because they have some success with making wordpress do what they want (after a fashion), or copy and paste some Javscript. That makes them a programmer, without knowing what they don't know, even 10 years later.
My current employers hire +- 1/100 applicants. The vast majority fall off before even getting to a coding test. Of the last 20, most are not fluent with conditional logic and iteration, or cannot use a dictionary in an algorithm. In the most recent interview, an "experienced" React developer could not set properties on a JS object.
