In some traditions, they want everyone to be similar. Some even prescribe dress and daily activities. Many ask you to believe the same things about the world, so you can all have the same mind and soul and all go to the same afterlife. Not all traditions, but many and most of those that populate American Churches.
Unitarian Universalism is different. We welcome your faith, your rituals, your voice of concern, of doubt, and even of dissent. We know that we are all going to end up together at the end of the universe, and we understand that our experiences give us each a different insight. We are thrilled to have people or all ages, all cultural backgrounds, and all levels of talent and skill. We accept you as you are, encourage you to be your personal best, and use what you bring to better the community.
Our diversity is not a failing; recognizing our differences means allowing us each to offer our individual strength. There is nothing wrong with admitting that while we are one species, there are divisions in language, culture, art, and thinking, and those differences make humanity more interesting and resilient.
A good team always requires mixing people with different skills and talents. A typical American Football team needs people who are large for blocking and hitting, a couple of people who can throw accurately over a long distance, and runners who can out maneuver the defenders and catch the ball. Likewise, a congregation needs people with diverse skills; people who can plan a worship service, people who can manage the upkeep on the building, and people who can teach RE. Diversity means each person can be good at a few things and count on others to help carry the rest.
Welcoming diversity is not a weakness, much less a failing. Welcoming people for who they are, who they know themselves to be, is what it means to be a Unitarian Universalist.