At least half the candidates I interview cannot figure out how to basically split a string. They all have years of SWE experience on their resumes.
One google interviewers ask me a question that starts with “implement google search” and ends with my implementing splitting a paragraph. Of course I failed the interview, but I have to think he has failed me way before we get to write any code.
I'd say about half of the candidates that interview are unfamiliar with the String#substring equivalent of their language. This is for a senior position, and everyone has multiple years of experience on their resume. It's... interesting.
Many people would say those candidates should be failed anyway due to X, Y, Z reasons. But I want to highlight that in those cases, the interviewers should realize they are assessing something else, and not programming skill.