I have interviewed many people employed in tech as programmers for their entire career and they can't code. I don't meen leetcode, I mean they get confused trying to write brute force substring search. The nested for loop seems to be too complex for them to keep in their head all at once.
I have had numerous people cry. Again this was a screen, not leetcode. I'm asking them to check if text has mismatched parens, or find a substring. Things you do for homework in your 2nd programming class freshman year. Things every competent programmer can do while chitchatting about the job.
I would estimate that more than 10% of screens are like this, again these are employed people in the industry for years, sometimes tens of years.
Edit: I understand that people can get flustered, I understand that some people have trouble under pressure or while being observed. That's why I pointed out multiple times that the problems I gave are extremely, EXTREMELY easy. I'm basically asking them to write down their name and they sit and look at the pen like they've never seen one before. If you can't write a 5 line function to find whether a substring occurs in a larger string when given 45 minutes, your choice of programming language, and as many attempts as you need to debug and try again you simply will not be able to do any useful work as a programmer. If you don't know that to match parens you need to use a stack (or at least that it's one way to do it) you either have a very poor memory or no training in computer science at all - either of which is frankly disqualifying. Anyone borderline competent would invent a stack when presented with this problem if they hadn't already been told this fact a dozen times during their education or even light reading about algorithms.