Fish don't climb but they swim.
Meaning that just because someone can't do one thing, doesn't necessarily mean they cannot do another.
Everyone has an area or field in which they will and can excel in, in comparison to other fields; in the fishes case; Swimming and Climbing.
Fish cannot climb, but they are great swimmers. The same way as some people have a mind for science and academics, where others are physically gifted. Not to say that both cannot exist within one entity, but usually that person will always excel in at least one area.
So don't judge others for what they cannot do or achieve, but instead; exalt them for what they can achieve.