> I never encountered a interview candidate so bad that they couldn't program fizzbuzz

Me neither, in the real world, but I have seen a couple of excruciating mock interview videos where the "candidate" was unable to complete the fizzbuzz task. I think this might be a result of people thinking that learning to be a developer involves following along with video tutorials on Udemy, and that as soon as some threshold is reached, they should be ready to look for work.