Am I the only one who doesn’t care if the team has one individual with such traits? Like, if it slows down execution, well, I’m not into squeezing the last drop of speed of everyone. Also, people like that always give you the chance to show how good you are (supposedly): you can support them with potential fixes, you can support the team by saying perhaps that the complaint is not a big deal because data says so, whatever.

It’s like those people who are racist: they always make me feel better with myself because I don’t hold such beliefs. If everyone would be a saint, I would feel a bit down (because I’m not one).

It's fine if you can ignore them and don't have to work with them. If you do it's really draining. Constant negativity is not fun to be around.

I have only worked with one person in my life who was really like this though, so maybe you're just lucky and haven't experienced a truly committed negative Nancy.