I don't remember being judgmental when I was a child, so I think we gradually learn to judge.
A child who spits out vegetables is being judgmental. A child who refuses to eat something that is green because he remembers his judgment about spinach is being prejudiced. Both judgment and prejudice are developed naturally at a very early age. All judgments are essentially present moment preferences. What you are talking about is saying preconceived ideas is not judgment. Preconceived judgments are prejudices.
We use similarity to past situations to evaluate the potential effects of new ones, so certainly that is learned. I guess I'm never sure if judgmental means to prejudge (i.e. without evaluating a current situation) or to just be very particular about things. As we age, I do agree we get lazier and tend to go with similarities, or lack thereof, to the past, instead of examining what’s in front of us.