I don't know how people manage to get "decades of industry experience designing and implementing very complex systems" without being able to program. I have only run into a couple such people, but I suspect that is because we get very few applicants with that kind of employment history.

I don't think >80% of programmers can't code. I think that programmers who can't code are much more likely to be applying for jobs than programmers who can code, which makes the pool of applicants look much worse than the pool of all programmers would look.

The 80% who can't code are hired by companies that don't test their skills, and there are lots of companies like that. Then they realize how much they suck, and lay them off whenever they get a chance. Most of these "bad" programmers write crappy (often insane) code that then good programmers have to deal with. Many of them delegate. I've even seen one guy outsource his work.

Most of the programmers looking for a job suck. If you're truly good and have a reputation, you don't need to interview (unless you want to work for a very specific niche where you don't have connections).