I will concede this though. When that bad person is a manager, EVERYONE on the team can suffer, the entire culture can suffer. When that person is just a team member, others on the team can usually figure out how to just avoid that person so that the problem can be compartmentalized. Better still, a good manager will not tolerate the bullshit because they know that it can poison the team if not handled properly. When that person is a manager, there's no avoiding the problem and team policies and culture will be poisoned accordingly so that the best people leave and nothing good is left.

It wouldn't surprise me to learn that a large number of users in this community have actually worked in a bubble of tech outside the norm where most devs were actually pretty solid overall. A developer who is truly incompetent (not just mediocre) would have a very hard time even getting hired at a FAANG or similar, let alone stick around very long.

The "old" saying (well, I've heard it said a few times) is: bad software (probably) won't kill your business. There's a litany of examples to this effect. However, bad management will, with increasingly leveraged effects the further that bad management is from the line worker.

They can also pester everyone with mountains of trivia in PRs and refuse to change anything in their own and so on and on.

My own boss says "the main thing is to hire nice people - everything else can be improved" and that changed my perspective a lot. I think he's right.

A bad EM can do more damage of course. :-)

I don't know how it is everywhere, but in my neck of the woods good developers are hard to recruit and expensive to lose - they have a lot of leverage and they know it.