The concept of cultural relativism does not really do either of these things. On the one hand, cultural relativism does not make one culture more likely to understand the other. At the same time, it is not as if the concept of cultural relativism prevents accords on issues such as human rights.
Cultural relativism is the idea that no one culture’s ways are morally better than another’s. In such a view, Saudi Arabia is not better or worse than the US because of the way it treats women. It is simply different. China is simply different because it does not believe in free speech. This does not promote cultural understanding because it simply paints other cultures as fundamentally different from us. They are, instead, portrayed as so different from us that they do not even share our most basic values.
At the same time, it is not as if all countries would agree on human rights if only the idea of cultural relativism did not exist. Instead, we would have a system where all cultures believed that their own view of human rights was fundamentally correct. They would have no reason to agree on human rights at all.
Thus, cultural relativism is neither as beneficial or as detrimental as some believe.