I have screened or interviewed hundreds of people over the past three decades. That is not a strong claim, it is simple truth. There is a large minority of so-called "professional" software developers who literally don't know what they're doing and can't anything but the dead simplest code.

They may only represent 2% of the population, but they are a much larger % of candidates searching for jobs. If you think about it a bit, you'll see why.