My hypothesis is that people like you who observe a negative correlation between competence and education only encounter such a phenomenon because you work for

My hypothesis is that people like you who observe a negative correlation between competence and education only encounter such a phenomenon because you work for employers who are not attractive to candidates who have better options. If your company has no name recognition and crap pay, then anyone who is both competent and has the right credentials will be able to get a much better job elsewhere. So your only coworkers will be either people who are competent but don't have a degree, and who can't leave for better pay because they won't pass a resume screen, or people have a CS degree but can't get hired at a more desirable company because they are incompetent. Hence the perceived negative correlation, which is entirely down to selection bias.