I've interviewed people who had ostensibly been working for years as a professional software developer be unable to even define a function that would accept a string as an argument, do _literally anything_ to it, and then return it. People who couldn't even write a syntactically valid function definition of any sort, during the entirety of an hour long interview, when given the choice to use any language they wanted.
A few years back I was working at a company that had a policy that they didn't have recruiters do any pre-screening of candidates who had prior development experience listed on their resumes. I was a frequent stage 1 interviewer for our team, and we gave the candidate an hour to write a function to count the occurrence of words in a string (e.g. "the old man and the sea" -> {"the":2, "old": 1, "man": 1, and" 1, "sea": 1}. Candidates were allowed to select any language they wanted, use their own editor/environment or use a cloud based IDE if they preferred. They were allowed to search any API documentation they wanted, to use any libraries, and were explicitly told to not worry about any edge cases like punctuation, capitalization, etc.
I'd guess about 1/2 of the candidates I interviewed were able to complete the assignment in the provided time, with about 1/4 of them finishing it almost immediately, and another 1/4 unable to even write a single syntactically valid statement or line of code. Some candidates claiming years of experience with a language couldn't even write something that looked at all like the syntax of the language.