Mediocre looks for “one size fits all.”
It’s been my experience, that humans; even ones that share much in common, have many different drivers, strengths, and limitations.
Culture also plays a big role. The US has a culture that encourages individual expression, and that’s one of our strengths (and limitations). We can get very good results, if we encourage individual expression, but it's really hard to manage. Irreplaceable people can add huge value to an organization, but they have to be correctly managed, and the organization needs to be structured to let them add that value.
I spent many years, working for a Japanese company, and their culture is a much better environment for “one size fits all.” In their case, it actually became a huge strength, but their approach would not work in the US.