Three of the four species are required to be beautiful. But the willow only need grow near water. It does not have to look like anything. The esrog has taste and smell and represents those who do Torah and mitzvos. The hadassah has smell and no taste. The lulav has taste (via the date fruit) and no smell. The willow has neither taste nor smell. It represents the simple Jew who doesn't do either. This is not the one who goes against commandments, but the one who doesn't know about them. Tinuk S'nishbeh. When you interact with such a person, "Don't set conditions. I want you to have this or that characteristic." Even the simple Jew is inherently connected to God as long as he is of the right species that grows near water. He is one of the four species without which you cannot do the mitzvah. The lulav is the Torah student. It is not enough for him to study. He must be bound up with the other species. When you approach another person, you cannot come with demands and say I will only help him if he fulfills the commandments. Approach him with love. He is a child of Avr, Yitz, and Yaakov.
The Rebbe said in response to a visitor who referred to ignorant Jews that his father in law would call them simple Jews.
Lub. Rebbe, Living Torah Program 683