The vast majority of people have the usual naive to criticize other people without knowing how those people really are, without first studying them, to realize that they are not perfect.
I see two possibilities that some criticize, though they do not know anything about the being they criticize.
The first possibility might be that they are too full of them and they have the impression that they are perfect and normal, and the problem is with the rest of the world.
And the second possibility is that they have too many defects and try to fool even themselves, leaving the impression that they are absolutely normal, judging others, believing that in this way their potential defects will no longer be revealed, and the world Will focus on the defects of others, and not on theirs.
My point is that we are all people and, therefore, we are wrong. Some more, others less. And that is why we should not criticize those around us, because that would mean to be perfect. And we are not!
See the beam in your eye, not the speck in the eye of another!