I can assure you that much of underperformance is a perception and miscommunication issue. If the employee is motivated and not stupid then if he's underperforming it's because objectives were not communicated or the manager failed to realize that the assignment was impossible not to underperform due to missing some challenging detail.
Many managers don't realize this. Even managers that have a ton of experience, all they do is fire or have harsh conversations with people who "underperform." The truth of the matter is a good manager is rare. 1 out of 10 literally and it's not an experience issue. A good manager is one who is highly highly unbiased and people are generally not like this.
The person you replied to is not a good manager. Based on his reply he is actually below average.
Basically for these managers good employees are those that can predict what the manager wants and how he thinks. If the person is able to guess and predict what his manager wants on a consistent basis, then objectives are more clear to this employee and as a result he can achieve them. These people are then perceived as "good employees".
Due note that a good manager makes objectives for each task unambiguous and crystal clear. A bad manager leaves a lot of room to fuzzy concepts like "quality of work" because he himself isn't clear about what he wants.
I have seen it many times. Employees who are basically geniuses fired because the manager wasn't able to realize how smart the person was. Instead the manager left the employee with vague instructions and expected him to just "get it." The manager didn't know that the employee is an expert in infrastructure and deployed him on writing algorithms...
This is an unwise and inefficient deployment of resources. It is the managers job to determine what each of his employees like and what they are exceptional at and deploy resources accordingly. It is also the managers job to understand in detail the nature of the assignment given to an employee so tasks can be handed out efficiently.
Bad managers tend to throw random people at random tasks without fully understanding the task or the person. In these cases there is an element of luck involved. How hard the task is versus if the person assigned to the task is suited for that task. An employee who handles the task well or is able to temper the expectations of the manager through communication is perceived as "good."
These managers are easily recognizable. I will tell you how to identify them. They perceive the world as employees who are "underperformers" and those who are not. The person you replied to put the world in 3 tiers lol. The world is very nuanced and it is impossible to divide people into three buckets like this. He is the quintessential example of "bad manager."