If you had this conversation in the real world instead of the internet, everyone would just say "yeah, duh".
It's rather simple. If you apply for a job and get hired because they like you, then the system is good. But if you apply to that job and don't get it, it turns into "fuck this old boys club". The outrage isn't logical, it's almost purely emotional.
I shouldn't have to say this but actual competence matters - without it at best you get stunted potential and mediocrity. At worst the whole thing falls apart like the cliqueish house of cards it is.
Why?
Most people are just trying to get by and enjoy life as much as they can.
I spend 40+ hours a week with the people I work with. I'm absolutely going to optimize for working with people I like more than their competence.
99% of us aren't working on life-or-death projects.
There are studies which show diverse teams are stronger because they bring in differing view points but I also think that they may end up self selecting for those that are empathetic enough to look through others eyes maybe.
Because in large companies you will not work with the people that hired you.
Many successful sport teams were composed by people who openly disliked each other, there's no reason to be likeable if you are not being paid to be liked by others, but there are many reasons to cooperate to the end goal if the team members' salaries depend on it.
For many people being likable in the way it is represented in the article it's more stressful and energy draining than the job itself.
I would go as far as to say that people that can't go through first impressions and work together with someone they don't particularly like (except of course if it's for good reasons) aren't good team members.
But they tend to select each other to not feel alone in being bad team members.
People are social beings. Part of working together comes from feeling like you want to cooperate. You could have someone who is incredibly smart and clever as your business partner, but will you really feel like you want to go the extra mile for him/her? Do you have to watch your back constantly? Do you have the same goals in life? Does every interaction drain energy from you?
We come from families, social structures. We have people in our families who are incompetent but we love them. It's not unreasonable to think that some of this behavior would continue in our work worlds.
"Diversity" in the trendy usage today, for most people still doesn't trump whether you want to work with someone, and that hopefully doesn't have much to do with race/background/gender/etc. I say hopefully of course, and helping people overcome or not be prejudiced that some characteristic correlates with ability/desire to work with them, is an important thing to do.
But forcing people to believe that someone's <x> characteristic is more important than whether you want to work with them is a recipe for dissatisfaction and backlash against people who insist that it should be so.