Maybe Evelyn has moved on because SHE was promoted due to incompetence. I've had only one manager in the 30 years that I have been working full time that did timely and regular performance reviews. So many managers view them as an unnecessary evil. How can one manage employees properly without them?

That doesn't excuse Eric. He's still a problem. The way to fix it is to do an immediate review, and corrective action plan, one that puts him on notice that his current performance is not acceptable, but which gives tangible ways that he can improve that performance. Chances are that it will not be effective long-term. But, at least it's the beginning of the end if it comes to that.

His mediocrity is likely evident to his coworkers. Putting up with it is poor for morale, and a waste of company money. If he doesn't improve, remove him and replace him with someone with a better work ethic and interpersonal skills. It's easier to train technical skills, that personality traits.

When I worked at Intel in the 90's there was definitely a philosophy of hiring the processor, not the program. Good processors are capable of running many different programs, but programs can't be easily fixed to solve a different task. In other words, hire good people, even if they don't have the complete set of technical skills. If you hire just for the technical skill, you have limited flexibility, and have to deal with the Eric's of the world.