In any team, there is often a sense of some people being better at their jobs, or performing at a higher-level than others. If they do it consistently enough and progressively tackle higher-level problems, that is a good indicator someone might be on track for a promotion.
If someone is good at their job, but doesn't really push themselves to improve, that might be ok for the time being depending on the role, it just means that person is less likely to advance, or advance as quickly as the former person.
And then you have people who are very clear underperforming. Whether it be lack of attention to detail, poor communication, letting things slip through the cracks, or just not doing their work. If you can work with them to improve in the areas needed, awesome. If not, you often need to get them off the team one way or another.
There is nothing dehumanizing about this. It is recognizing people's strengths and weaknesses, and trying to optimize accordingly for the best outcome. Further, to pretend that this dichotomy does not exist is sticking your head in the sand.
At the end of the day, regardless of the category these individuals fall into, they are people, and I never said otherwise, so I don't appreciate you trying to paint me as such. Not all humans are equal at their jobs, and if you can't identify that and adjust your management style and approach accordingly, you can't be a successful manager.